Introduction - Josh Taborjoshtabor.com/docs/classes/secondyear/drillingandwell/drillingnotes.pdfa....

Purpose

Boreholes are drilled and wells are constructed for many reasons in different settings○

There are many drilling methods○

Drilling & well construction is a large and important industry-

Factors Affecting the best drilling method for a given setting:

Sedimentaryi.Crystallineii.Igneousiii.Metamorphiciv.

Consolidated Rocka.

Compressive Strength - Force/Unit area needed to deform a material; Deform = change in materials shape or volume).

1)

Brittle Deformation - High Force on Bit is requireda)Plastic Deformation - High RPM is best; ex. Clay Materialb)Ductile Deformation - An in-between of Brittle and Ductile deformation.

c)

Mechanical Behaviour - Brittle, Plastic, Ductile2)

These materials have different compressive strengths and mechanical behaviouri.Unconsolidated sedimentsb.

Geology1.

Larger diameter holes require specialized equipment. a.Deep holes require the drilling rig to be capable of both reaching great depths and the pulling capability (getting the bit out of the hole).

b.

Hole depth & Diameter2.

Remote areas or difficult areas to get into will require different drilling rigs. Large drilling rigs may not be able to get into a certain area.

a.Location3.

Price of drilling the hole or well can be excessive. Consideration of the price of drilling and the price of casing must be considered.

a.Economics4.

Consideration of the pulling capability of the rig dictates the depth of the hole or well.

i.Type of drilling rig or size of equipment is going to dictate the scope of the project. a.

Equipment Availability5.

Is the hole going to be a drinking well, geotechnical well, for resource exploration, etc.a.Reason for drilling the hole/well6.

Example reasons for drilling holes & wells into the subsurface

Often split-spoon sampling1)Subsurface composition information for construction.i.

Geotechnical Drillinga.

Water, oil & gas, minerals, coal bed methane, geothermal resources.i.Resource exploration & evaluationb.

Installation of monitoring wellsi.Environmental Drillingc.

Gain information1.

Exploiting a resource2.

IntroductionSeptember 13, 2015 9:53 PM

Drilling and Wells

Oil & Gas, mining, and quarrying.a.Exploiting a resource2.

Constructing blast holes, pipeline installation, cable installation, remediation of contaminated soils, subways, wastewater collection systems, etc.

a.Other3.

Drilling and Wells

Percussive a.Rotativeb.

Two broad categories of drilling methods-

Based on the type of bit motion at the bottom of the hole.-

The bit has a primarily reciprocal up and down motion.i.Fragments are produced by impact energy by the bit on the formation.ii.Very rapid percussive motion.iii.

Down-the-hole hammer drill method is very common in Halifax area. 1)Examples: pneumatic rock drills, down-the-hole hammer drills, & cable tool rigsiv.

Percussivea.

The bit rotates on the bottom of the hole.i.

Dependant on the formation material strength and mechanical behaviour.1)Fragments are produced by high Force on Bit or a combination of FOB & RPM.ii.

Examples: Augers, hydraulic rotary rigsiii.

Rotativeb.

Relies on compressive pulses being transmitted through the bit.(i)Air-driven piston engages the top of the drill rod.(ii)Strong drill rods with small central air duct. (iii)Rotating mechanism(iv)Coupled rods added to allow deeper drilling. (v)

Advantages○

Reduced ROP with depth becomes uneconomical 1.Hole depthi.

Limited by annular cleaning capability1.Hole Diameterii.

Low strength formations impede rotationiii.Four inch holes to ~175 feet.iv.

Limitations ○

Pneumatic Rock Drills-

Elements: An air hammer is installed in the hole immediately above the bit with independent rotation from the surface.

○

Greater depthsi.Ability to pass large volumes of air down the rod and back through the annular space.ii.

Routinely 9" holes for sever hundred or even thousands of feet.1.Larger hole diameteriii.

Advantages○

Lifting capabilities of the drilling rig when extracting the rods.1.Limitations○

Down-The-Hole Hammer Drills-

Compressor

Drill Rod

Drill Rod Annular Space

Drilling MethodsSeptember 15, 2015 8:52 PM

Drilling and Wells

The bit and stem is suspended by a wire rope & cable○

Just as the bit approaches the bottom of the hole the cable is then pulled up causing the wire rope to be stretched, causing the bit to quickly snap on the bottom of the hole.

i.The bit and drill stem is repeatedly raised and lowered by means of a walking beam/spudding beam.○

The bit delivers impact energy to the formation.○

Let's the bit twist allowing for rotation.

Allows for elasticity1.Cable used is 6x18 left-lay cable-wire rope.i.

Rotation is facilitated by the wire rope construction and swivel socket along with variation in cable tension.○

Cuttings are removed in the form of a slurry using a dart valve bailer.i.No flushing fluid is used.○

In unconsolidated formations casing is driven as drilling proceeds to keep the hole open. ○

Cable Tool Drills-

Requirements are Thrust & Feed, Rotation, and Flushing.○

A constant force is applied to the bit so it can penetrate the formation.1.The bit is fed forward as cuttings are removed by a flushing fluid.2.

A constant force is applied to the biti.

Often water based1.If the bit isn't constantly fed forward the FOB will drop2.

Cutting are removed by a flushing fluidii.

Two things dependentForce/Unit area needed to deform a material; Deform = change in materials shape or volume).1.

Formation compressive strength iii.

Thrust & Feed○

(Direct) Rotary Drilling-

Drill Rod Annular Space

Hammer

Drill Bit

Drilling and Wells

Higher porosity = Lower Density = Lower Compressive Strength

Lower porosity = Higher Density = Higher Compressive Strength

Formation Porosity (density)◊

Higher consolidation = Higher compressive strength

Lower consolidation = Lower compressive strength

Consolidation◊

Two things dependent

Crushing is best

Operation - High FOB & Low Rotary Speed (RPM)◊

High Strength Brittle Rock

Shearing is best

Use of high strength bit would tear teeth off bit

Operation - High RPM & Low FOB◊

Low Strength Plastic Material

Operation - Combination of RPM & FOB◊

Ductile Material

Formation compressive strength and mechanical behaviour dictate bit design and operation.1.

Large Diameter, thick walled pipe.

Drill collar provides all FOB–

If it is above the drill collar the drill pipe with flex back and forth causing it to break off.

Neutral Point must be in the drill collar–

Force on Bit (FOB)

Stability to the bit

Straight hole with less deviation

Function of Drill Collars (Pg 260).◊

Allows passing of drill fluid upwards

If the sides of the hole close in, it reduces the pull requirements to get bit out of the hole.

–

Reduced surface area

Spiralled Drill Collars◊

Applied Weight of the drill string1.

Compression is the whole length of the drill pipe.1.Drill pipe must be thicker (stronger).First.

Making use of the weight of the drilling rig itself.One.Pull Down Chainsi)

Hydraulic Pull Downii)

Applied force from the ground surface2.

Sources of Bit Thrust2.

Thrust (FOB) has to overcome formation compressive strength depending on Formation Porosity (Density) and Compressive Strength:

iv.

Functions to expose new material to bit.

Contributes to fragment production in low compressive strength plastic material.

Also called a Kelly Drive

Provides lots of rotary torque.

Example:

Rotary (Drive) Table□Rotation is provided by

Rotation○

Drilling and Wells

Hydraulic motor at the top of the drill stem (Pg 254)

No Kelly Drive◊

Less torque than Kelly Drive system.◊

Both pull down & hydraulic motor

Top Head Drive□

A compressor is used.

Dry Air

Provides a small stream of water to the airflow.◊

Lowers the possibility of contaminating the well with pathogens or chemicals from untreated water.

Requires a service truck with treated water in order to function.◊

Mist

Like a detergent

Surfactant breaks down water into atoms or very small particles which allows the water to be 'lighter'.

Add surfactant to a mist◊

Foam

They act as viscosifiers.

Bentonite is a type of clay.

In this instance, the use of an oil based flushing fluid is often used. –

Under high temperatures and pressure the B & P break down and become useless.

Add polymer & bentonite to a foam.◊

Stiff Foam

Adding surfactant, polymers, and bentonite helps with Slip Velocity; the difference in air velocity vs. particle velocity in the annular space.

Air-Based □

Re-circulated by a piston pump.

Requires a settling pond or setting tank so that drilling particles aren't sent down into the well or hole.

Water-Based□

A flushing fluid conducts loose material away from the bit and to the surface through the annulus.

Flushing○

Greater velocity, better carrying capacity□Turbulent flow is best□

Function of annular velocity

Carrying capacity of fluid.○

Major Concerns of Flushing Fluids-

Drilling and Wells

Turbulent flow is best□

Dependent on compressor or pumps output□Cross sectional area of Annulus□

Annular Velocity

□

Thicker = better carrying capacity

Bentonite added to increase viscosity

Increase in Velocity = Decrease in Viscosity Requirements

Decrease in Velocity = Increase in Viscosity Requirements

Resistance to Flow□Viscosity

Higher the density = better carrying capacity□Never used to increase the carrying capacity (only annular velocity and viscosity)□

Density

Pressure exerted by a column of fluid at depth

100ft x 8.33 ppg x 0.052

□

Water Constant= 8.33 ppg or 1000 kg/

Bentonite Fluid Density = 8.65 ppg

Hydrostatic Pressure○

Down hole pressure control-

The pressure exerted by the formation pore fluids○

Hydrostatic pressure starts at the water table○

Formation (Pore) Pressure-

Formation Permeability Exists1.The pore pressure exceeds the borehole hydrostatic pressure2.

The well will flow with the pump off if ○

Drilling fluid will be lost in the porous formation□Formation pressure is less than borehole pressure1.

Loss of circulation

An excessive borehole pressure is detrimental○

Drilling and Wells

Formation pressure is less than borehole pressure1.Formation permeability2.

Fragments are re-chipped by drill bit

Due to chip hold down□Reduced Rate of Penetration

Complete hydrostatic connection from top of water table to depth

Produce water by gravity drainage from an area of higher to lower potential energy

Unconfined Aquifer ○

Hydraulically impermeable (to water)

Shale or Clay

Confining Layer○

Hydraulically impermeable (to water)

Shale or Clay

Lower Confining Layer○

Characterized by an overlying hydraulic barrier (i.e. upper confining layer) such that as overburden thickness increases, the water in the aquifer pores cannot get squeezed out

Water moves from areas of higher to lower pressure□Pore spaces are saturated due to pore pressure□

Produce water by aquifer compression

Aquifer material compacts with overburden thickness and the water in the aquifer pores gets squeezed out (moves towards the area of discharge)

Ex. Mexico and San Francisco ◊

Causes settling

Moving water from confined aquifers causes compaction□

The confined aquifer can rebound if allowed to recharge because it is somewhat elastic□

The aquifer material is therefore under compacted and the pore water starts to assume a portion of the weight of the overlying overburden

The unconfined aquifer does not have complete grain to grain contact

Recharge in the mined aquifers is negligible□25% of sea level increase can be attributed to aquifer mining

Confined Aquifer○

Unconfined vs. Confined Aquifers-

Drilling and Wells

Classified as a non-flowing artesian well

The potentiometric surface can be below the ground surface□

Classified as a flowing artesian well

Flowing conditions are when the potentiometric surface is above the surface□

If the top of the aquifer is above the water table you have artesian conditions

Artesian Conditions□

Sometimes there may not be an unconfined aquifer□

Potentiometric Surface

They can plug off the formation permeability□Preventing Bentonite, Polymer, Liquid, Formation Clays, silts, and sands from entering the formation

Prevents formation (producing zone) contamination○

The loss of the water through small formation openings (pores)□Filtrate Loss

The loss of the whole drilling fluid□Loss of drilling fluid through large formation openings□

Lost Circulation

Filtrate loss vs. Lost Circulation○

Gold balls, large bentonite, gravel, hay, sawdust, walnut shells, cotton shells□You cannot continue to drill as is; stopping to add a lost circulation material is required

Minimizes any fluid loss or lost circulation

Uses lost circulation material

A thin, tough, impermeable layer that forms on the borehole wall

Permeability of Formation1.Overbalance in pressure2.

Requires two things

Initial spurt loss followed by suspended solids getting filtered out

Filter Cake Formation○

Fluid Loss Control-

Minimize torque on the drill stem

Bentonite & polymer fluids are "slippery"

Cool & lubricate the bit & stem○

Permit removal of cuttings at surface○

Ensuring that on the first trip to surface contains fresh drilling material□Sediment samples

Facilitate getting good borehole information○

Gel structure of bentonite fluids; thixotropic gel structure

Keeping cuttings suspended in the borehole when the pump is shut off○

Other functions of Drilling Fluids-

Drilling and Wells

Gel structure of bentonite fluids; thixotropic gel structure

Keeps sediment out of well water.

Allows water to pass into the well.

Installed in semi-consolidated material○

Wellscreen -

Keeps pump twisting motion from transferring to the pipe.○

Installed directly above the submersible pump. ○

Torque Arrester-

Used to remove the fine particulate from around the well casing and replaces it with larger grained particles. ○

Achieved through methods like pumping air down the well and into the annular space. As the air rises it expands and brings water up which flushes out the fine particulate in the annular space.

○

Named: Sand pack, gravel pack, or filter pack.

The use of pea gravel is done when the formation is uniform in size; fine grained material.○

Developing a well naturally requires material to be widely ranged in size.○

Developing a Well-

Blow Out Preventer○

Borehole is sealed at the top, allowing the pressure changes in the borehole to be measured○

If gas is released by the formation, it will expand as it rises and cause a blowout○

BOP-

Hole is the proper diameter

Used to ensure drilling is happening at the right gauge○

The drill bit can drill under gauged causing the next drill bit to get stuck in the bore hole ○

Reamer-

Drilling and Wells

Keeps the casing perfectly centered in the borehole○

Commonly used in the water well and monitoring well industries○

Centralizer-

Drilling and Wells

Plastic - Water Well

Steel - Oil & Gas

Commonly Steel or Plastic○

Minimum 20' in Well Construction Regulations of the NS Environment Act

Necessary component of any well construction○

Allows installation (telescoping) of 4" liner inside the 6" casing□NS Environment Act requires 6" casing for this reason

If you have cracks or fractures in the bedrock into the bore hole you may need to install a liner to prevent leaking

○

Casing is installed in a borehole for various reasons-

Drill to depth and lower into hole

Enforced by Inspector Specialist□Minimum 20' in Well Construction Regulations of the NS Environment Act

Gap left between casing and borehole is grouted□Necessary for tight seal□Required to be grouted to bedrock□Lessens the degradation of the well casing; mainly in the case of steel casing□

Commonly grouted

Installation○

Minimize hole erosion & caving□Maintain hole integrity

Loss of drilling fluid into the formation□Prevent lost circulation

Prevents highly turbid water from forming in the well due to surface water contamination

□Protect the water supply

Well screen is tied or screwed into the bottom of the well casing and lowered into the bore hole

□Used in combination with well screens in unconsolidated formations

Purpose○

Hydraulic Rotary Drilling-

Method of choice locally in Nova Scotia○

Drill to depth required

Use of pull down chains is required

Push□

Cap placed on top of casing and hammer drill hammers it into place

Casing shoe is used to seal the casing to the formation

Welded onto steel casing

Hammer□

Grouted if lowered into place

Lower□

Push/hammer/lower into place

Installation○





Purpose○

Down-the-Hole Hammer-

Well CasingSeptember 28, 2015 9:25 PM

Drilling and Wells

contamination



Must drive casing as you go through unconsolidated material□Once you hit bedrock you no longer need casing□Temporary casing is used until the grout is placed then then it is removed□

Drive and/or lower into place

The well is then developed

After developing the well, it is then grouted

Casing is driven into the unconsolidated material layer, sandy layers, then the bailer gets a representative sample allowing the proper well screen gauge size. Once the screen is selected it is telescoped in and the casing is then pulled back up to the top of the sandy layer.

□Pull back method

Installation○







Purpose○

Cable Tool Drilling-

In combination with grout: casing isolates the zone from which a representative groundwater sample can be collected

○

Rounded quartz sand□Filter pack is placed around the well screen

2" PVC pipe is used with a 2" PVC well screen○

Top of well must have a concrete pad to prevent surface water contamination from entering through the bentonite grout

○

A large borehole is drilled and two or more well casing pipes are lowered into different layers in the formation.

A multi-level well○

Monitoring Wells-

Drilling and Wells

Cover overburden from unconsolidated material○

Minimize hole erosion & caving□Maintain hole integrity ○

Loss of drilling fluid into the formation□Prevent lost circulation○

Mineral Exploration-

Several casing strings can be installed; all of which are grouted with Portland cement ○

Drill the hole and then lower casing into place□Acts as a conduit between the surface and more competent formation at depth

□

Minimize hole erosion & caving

Maintain hole integrity □

Loss of drilling fluid into the formation

Prevent lost circulation□

Conductor Pipe□

Covers aquifers: keeps out oil and gas from contaminating the aquifer□Maintains hole integrity□Minimizes lost circulation□Means to attach Blow Out Preventers□Down the hole pressure control□

Surface Casing□

Intermediate Casing□

Hangs off the intermediate casing by means of a liner hanger□Cemented into place□

Liner□

Conductor Pipe, Surface casing, intermediate casing, liner○

Oil & Gas Wells and Deep Water Wells-

Drilling and Wells

Cemented into place□

Pressure exerted by the fluids in the formation pore spaces□Pore (Formation Pressure)○

Hydraulic pressure needed to fracture the formation□Fluid acts as a wedge between grains; forces them apart□Done to stimulate oil & gas wells for greater production capabilities□

Formation Fracture Pressure○

Every area has a pressure gradient associated with it□Dependent on salinity□

Pressure Profile○

Not always a constant pressure gradient at depth due to changing salinity□

In other words, the pressure at depth expressed in terms of the drilling fluid density to exactly balance it

□

Formation pressure can also be expressed in terms of an equivalent drilling fluid density

□

Equivalent Drilling Fluid Density○

Confined Aquifers are an example of an over pressured formation□The Pore pressure = hydrostatic pressure + some portion of the weight of the overlying overburden

□

Formation material is under-compacted□A hydraulic seal is formed by rapid sedimentation □

The well may kick1.Drilling into an over-pressured zone□

Over pressured formations○

Down-Hole Pressure Control-

Drilling and Wells

The well may kick1.

Where fracture pressure is exceeded by drilling pressure, casing is needed

a)

The drilling fluid needed to control formation may exceed the fracture pressure below the previously installed casing

2.

Underbalanced a)Formation permeabilityb)

Brought to surface with no control◊

Hydrostatic pressure = 5200 psi

(5200psi)(1) = (14.7psi)(V2) –

P1 V1 = P2 V2

Boyles Law◊

Example - A gas kick at 10000ft, drilling fluid density is 10.0ppg without a blowout preventer or compensation of any kind

Bottom hole pressure = hydrostatic pressure exerted by the drilling fluid below the bubble + 5200psi exerted by the bubble

◊

HP = 5000ft x 10ppg x 0.052 = 2600psi

5200psi + 2600psi = 7800psi at the bottom of the hole

When the gas bubble is at 5000ft the bottom of the hole pressure will be the pressure exerted by the gas bubble + the hydrostatic pressure

◊

HP = 10000ft x 10.0ppg x 0.052 = 5200psi

BubbleP = 10000ft x 10.0ppg x 0.052 = 5200psi

HP + BubbleP = 10400psi

If the gas bubble is at the top the fluid density required to continue drilling balanced would be:

◊

Example - A gas kick at 10000ft, drilling fluid density is 10.0ppg with a closed blowout preventer but no compensation allowing the gas bubble to rise

Gas kick is the worst type of kick□

Kick - Influx of formation fluids into the borehole□

Drilling and Wells

Leak off Test□

Sandstone is porous and weakest as far as fracture is concerneda)Set casing and drill into first sandstone unit1.

Close the BOPs and Pump slowly2.Monitor pump pressures3.

Determination of Fracture Pressure□

Tells you the max fluid density you can use before fracturing the formation

Test does not ruin integrity of formation, when pump is shut off and BOP is opened the fractures will close off again and fit together like a glove

Formation fracture pressure = hydrostatic pressure exerted by the drilling fluid + the leak off pressure

□

Pump slowly and build drilling fluid density◊

Now that the formation pressure is known (from the shut in pressure) and the formation fracture pressure is known (from the leak off test). The gas kick can be safely circulated out by balancing the two pressures and allowing for controlled expansion of the gas

Well Control□

Drilling and Wells

Drilling and Wells

Been practiced since 1949-

Can be beads, sand, plastic balls

To keep factures open they use a proppant ○

Opens up fractures and the drill fluid acts as a wedge-

Fracturing has become more controversial because it has been combined with directional drilling

-

When fracking was first practiced it was only used on vertical boreholes which limited the area that was being fracked

○

Now, fracking is practiced on the horizontal for several thousand feet which drastically enhances the area affected

○

Over 600 chemicals-

Slick water is added to minimize fluid friction loss□

Fluid Friction Loss - pressure lost due to frictional loss as it moves from point A to point B

They control viscosity, control corrosion, control pH, bactericides, control friction loss○

Fracking takes up millions of gallons of water-

Backwash○

Mineral dissolution leading to brine water formation□Water in pore space was already salt water & it was in contact with subsurface

Frack fluid chemicals

Plankton pick it up while they are alive and fall to the ocean floor

Organic material accumulate uranium 235 & 238□

Cation exchange adsorbed K in both radioactive (0.01%) and non-radioactive (99.99%)

K40 & Th232 - Accumulated by clays & formed into shales□

Shale layers can be identified by their gamma rays□

Radioactive

Getting rid of backwash fluid by means of injecting it into the subsurface○

Hydro Fracking October 4, 2015 11:57 PM

Drilling and Wells

Aquifers-

Grout jobs around the casing shoe

If the grout job on the casing is bad, then aquifer contamination can happen○

Hydro Fracturing Water Wells-

Proppant is not required in water wells (in most cases) because the fractures are being developed not created

The fracking fluid used is water○

The extent and interconnectedness of the existing fractures will increase○

Rock weights 19.2 ppg & Bulk Density = 2.3 g/cc with pore spaces○

Silicate minerals = particle density of 2.6 g/cc○

Anything above this lifts the fractures○

= Applied pump pressure○

○

Drilling and Wells

Hoisting System○

Circulation System○

Rotary System○

Blow Out Preventers (Oil and Gas Rigs)○

Three Main Systems-

Rig Components-

Pulley system associated with drill line

Crown Block & Water Table○

The tower itself

Hoisted up with the hoisting system

Mast○

Someone stands on the monkey board to take drill pipe out of the ground

Can be a single, double, or triple drill stem removal system□Used to take two or more lengths of pipe out of the ground at a time

Monkey Board○

Large block & tackle system

The line is called a 'deadline' which leads down to the 'deadline anchor' on the lower level of the rig

□

The 'fastline' is the supply line to the system; it moves□

Leads back and forth to the crown block & draw-works; it does not move

The more lines on the travelling block means the more hoisting power

Travelling Block○

Allows the drill stem & Kelly to rotate

Swivel○

Used to latch onto the pipe as it is hoisted over to the borehole

Elevators○

Square pipe that fits into the kelly bushing

Kelly○

Fits into the rotary table (master bushing)

Kelly Bushing○

Where the next piece of drill pipe is stored

Pipe goes up the catwalk and then up the pipe ramp

Mousehole○

Where the Kelly, Kelly Bushing, and swivel is stored when new pipe is being installed or removed

Rathole ○

Used to make pipe connections

Makeup & Backup Tongs○

Hoisting mechanism

Drawworks ○

Two dials (FOB & String Weight)

Greater the strain on deadline = greater strain on bit□Done with the strain gauge on the deadline

If the weight displayed is greater than it should be, then the bit is stuck in the hole

Weight Indicator○

Monitors: Brake handle, FOB, RPM of the pump, Pump Pressure, Drill fluid in/drill fluid out

Drillers Console○

Includes recordings of all readings□ROP is calculated from the office□

Drillers office

Doghouse ○

Also known as the Kelly House

Rotary Hose○

Stand pipe goes up the mast and supplied the drill pipe with drill fluid

Flexible allowing for movement vertically or horizontally

Stand Pipe○

Filled with nitrogen gas and used to fill the BOPs.

Accumulator Unit○

Direct Hydraulic Rotary RigOctober 5, 2015 10:26 PM

Drilling and Wells

Filled with nitrogen gas and used to fill the BOPs.

Nitrogen doesn’t burn; is an inert gas

Elevates the drill rig to accommodate the BOPs

Substructure○

Drill fluid coming to surface flows to mud return tank via gravity through this line

This process is called the "Drill Fluid Conditioner"□

Goes from mud return line to shale shaker, shale shaker to settling pit, settling pit to desander/desilter where particles are spun out

Mud Return Line○

Loop of metal at the top of the drill string

Bail○

Part of the BOPs

System of pipes & valves

Has redundant values for when one gets worn out due to abrasiveness of the gases

Choke Manifold○

System of baffles

Mud/Gas Separator○

Takes out any remaining gas by means of agitation & negative pressure

Degasser○

Waste disposal

Drill cuttings & drill fluids

Reserve Pit○

Where all the bentonite etc. is added to the system

Mud House○

Drilling and Wells

Drilling and Wells

Best for consolidated material

Compressor - for air based drilling○

Creates the mist in air based drilling systems

Injector - for air based drilling○

For unconsolidated material

Mud Pump - for water based drilling○

Can flip between air based & water based drill fluids-

How a water pump creates the pressure

More stages = more pumping pressure□Each impeller/diffuser combination is called a stage

Impellers/Diffusers ○

Without check valve you will get a hammer effect

Keeps the water column in the pump when the pump is turned off

Check Valve○

Keeps the pump from twisting in the well casing

Torque Arrester○

Powers the electric pump

Should be tied off to the pump column every 10 feet

Electric Cable○

Can cause the loss of the location of the well (new regulations, since 1980, require that the well cap be 6" above the surface of the ground)

Buried water wells are susceptible to surface water infiltration which will cause positive coliform counts

□Advantages to a pitless adapter

Allows for wells to be completed above ground level (can be found)□Provides a tight seal between the casing and the horizontal line□

Uses a T-Bar adapter for access to the well and pump column

Allows easy access to the well & pump□

Three Advantages

Pitless Adapters○

Earwigs like the damp cool air in the well casing and when they fall in the well you will get a positive coliform count

□Vermin proof

To replace the water in the well that is removed when the pump is turned on

□

The bacteria, lithotrophs, oxidize available sulfur ions due to the lack of oxygen. Many times the bacteria are using Calcium Sulfate, , which is reduced to ions

Causes things like Sulfur Reducing Bacteria to live in the well◊

Prevents anaerobic conditions

To maintain aerobic conditions□

Well cap vent has to be of adequate size

Well Cap○

Provides a reservoir of water

Without a bladder in the tank you would have air dissolving into the water (old tanks did not have the rubber bladder and air would have to be added every once in a while)

□Provides a reservoir of pressure

30/50 or 30/60 psi pump settings□Tanks make it so the pump doesn't always have to turn on to provide flow

Air Tank○

Components in a well pump-

Water Well DrillingTuesday, October 06, 2015 12:49 PM

Drilling and Wells

30/50 or 30/60 psi pump settings□

Deliver water to point of use

Well Storage = water stored in the well

Aquifer Storage = water stored in the formation

Allows water to flow through the formation and into the well□

By turning on the pump, the water flows from an area of high PE to low PE

◊

Water is flowing from an area of high to low potential energy

Drawn down curve represents the lowered water table

Unconfined Aquifer□

Water flows from and area of high pressure to low pressure

Draw down level represents the pressure level

Confined Aquifer□

Lowers the water in the well

2.31ft/psi & 0.102 m/kPa = Head pressure

Pressure expressed in terms of the height of a column of water◊

Head is used as a measure of pressure (unit)

Pressure needed to move water against frictional force◊

Pressure Energy

Pumps rely on velocity energy to pressure energy (and back and forth)

◊

Velocity Energy

Head Energy (potential energy)□Pumps impart energy to a fluid

Pumps act to○

Water Well Pumps-

Drilling and Wells

Shallow well - at well surface

Deep well - in well column

Location○

Positive Displacement

Variable Displacement

Engineering Design○

Pump classification-

Atmospheric pressure acting on the free surface of the well

This makes use of atmospheric pressure to drive the water up the pipe□

Max theoretical life 0.433 psi/ft or 2.31 ft/psi□

Friction pressure loss

Water boils when pressure acting on the water falls below the vapour pressure of the water

–

Boils

The water in the pump will cavitate◊

Cannot create a perfect vacuum

Max practical lift ~22-24ft□

The pump operates by creating a negative pressure

Located above ground and pump water by means of suction lift○

Shallow well pumps-

PumpsTuesday, October 13, 2015 1:07 PM

Drilling and Wells

Atmospheric-cavitation - Water will have cavities of vapour because the atmospheric pressure is less than the vapour pressure

◊

Minimum pressure that must be maintained on the water to prevent boiling/cavitation

Hydrostatic pressure + Atmospheric pressure + Friction pressure = Absolute pressure acting on the water

Because of this potential vacuum you must create a net positive suction head◊

Located in the well submerged in the water column○

The pump builds pressure on the water which drives the water to the surface○

Can be used for any practical lift requirements○

Deep Well Pumps -

As the gate is closed the pump slows down□Discharge remains constant regardless of the head against which the pump is operating

Positive Displacement Pump○

As the gate is closed the pump slows down□Discharge is inversely proportionate to the head against which the pump is operating

Lift head - Static Water Level (SWL) + Draw Down = Change in Pulled Water Level + Static Water Level

□In a water well you have a total dynamic head

Fluid viscosity, density, flow density, flow system configuration (pipe diameter, elbows, material pipe is made of) and flow regime (laminar flow vs turbulent flow)

□Friction Head

Can be both shallow wells or deep wells□Most well pumps are of the variable displacement type

Variable Displacement Pump○

Engineering Design-

Pressure energy & velocity energy are inversely proportional

Rely on the Bernoulli Effect○

Variable Displacement Pumps-

Drilling and Wells

Pressure energy & velocity energy are inversely proportional

More Examples of the Bernoulli Effect: Saltation (Lift & Bounce), Wing, and an Aspirator

Make use of high velocity imposed on the water by means of the centrifugal motion of spinning impellers.○

The water is discharged from the impeller to an adjacent stationary diffuser○

The velocity on the water slows & velocity energy is transformed into pressure energy○

That is the pressure that drives the water to the surface○

An impeller/diffuser combination in a pump is called a stage○

Total dynamic head requirement is dictated by the number of stages required○

Low pressure on the water at the impeller causes a negative pressure condition that allows continued intake at the impeller "eye" (where water comes in)

○

Works like a diffuser

Less susceptible to clogging

Volute - allows the water velocity to slow which builds the pressure○

There are enclosed impellers & open impellers○

Minimum pressure that has to be held on the water at the pump intake to prevent boiling

Bubbled behind a boat is actually boiling due to the high velocity acting on the water, causing the pressure to fall blow atmospheric pressure

Must maintain a net positive suction head○

Centrifugal Pumps-

Jet Pumps-

Drilling and Wells

Variable displacement pump○

Combination of centrifugal pump & venturi nozzle○

Jet Pumps-

Drilling and Wells

Abrasiveness - Angular coarse sand can wear a bit down quickly

Quartzite can also wear a bit down quickly

Based on formation compressive strength, mechanical behaviour, and abrasiveness○

Compressive force per area needed for deformation

Function of formation porosity and consolidation

Compressive Strength○

Mechanical Behaviour○

Bit selection and operation (FOB/RPM) is critical to drilling economics -

Steel blades

Hardness greater than quartz□May be hard-faced with tungsten carbide

Suitable for unconsolidated (low compressive strength) formations

Drilling requires both thrusting and shearing action

Cheap bits for drilling

Sometimes called wing bits

Drag Bits○

Bit face is impregnated with synthetic diamonds

Polycrystalline Diamond Compact (PDC) Bits○

Bit Types-

Drill BitsOctober 15, 2015 12:57 AM

Drilling and Wells

Drilling and Wells

Bit face is impregnated with synthetic diamonds

Can drill in a wide variety of materials

Very expensive bits (over $100,000)

Tooth size, shape, and spacing is manipulated along with bit operation to accommodate different formation types

Larger, longer, widely-spaced teeth□

High FOB due to the build of the bit

Low RPM due to cutting back on torque

High FOB, low RPM□

In lower strength, unconsolidated formations and sedimentary rocks:

Many, closely-spaced, small diamonds□

High FOB would just knock the diamonds off the bit◊

Shearing the formation

High RPM, low FOB□

Small diamond dimples make up cutting surface□RPM can be 600-700 RPM□

In high strength, abrasive, crystalline rock:

Variation of PDC bit type

Hollow bits that allow a cylinder of rock to pass through into a core barrel

Once the core is lowered to the depth where a core will be taken, a ball bearing is dropped down the bit to the top of the cone.

A core catcher keeps the core in the core barrel

If the formation is fractured, a complete core may not be attainable

Very expensive method due to the down time because of the need to take the drill string out of the well repeatedly to change bits

Wireline core bits, suitable for shallow wells, use a line of wire to close the core catcher latch

Core Bits○

Drilling and Wells

Drilling and Wells

in textbook

Air percussive drilling in consolidated, high compressive strength, brittle rock

Cutting structure consists of tungsten carbide buttons

Rapid reciprocal motion (1800-2100 BPM) driven by a pneumatic hammer

FOB low, low RPM (10-30)

Formation fragments from bit impact energy

Down Hole Hammer Bit○

Granites can be drilled but not at the best efficiency□Suitable for all but the highest of compressive strengths

Cutters, bearings, bit body

Consist of three conical cutters mounted on bearings which run on pins which are part of the bit body

□

Mill (Steel) Tooth

Tungsten carbide "button" bits

Two types□

Can be changed to optimize the hydraulics

Nozzles□

This helps keep the bit clean◊

Teeth from one row fit into place into the space of the other row

Teeth□

Elements

Tri-Cone Rock Bits○

Drilling and Wells

Drilling and Wells

Start with a smaller diameter bit and then use a reamer bit to make the hole larger

Pilot hole is the first hole drilled

Mainly used for drilling stepped wells (oil and gas)

Roller Cone Reamer Bits○

Can be used to make a space large enough for the filter pack & drill casing to be installed□Used to drill an open hole larger than the drill casing

Eccentric bit comes out when you rotate the bit to the right.

Eccentric bit goes back in when you rotate the bit to the left

Eccentric Bit○

Cutter design and bit operation are manipulated to accommodate drilling in different formation types○

Tooth size, shape, spacing, and material

Cone geometry

Cutter design:○

Cutters-

Drilling and Wells

Drilling and Wells

Cone surfaces□

Cone centerlines are offset in the direction of bit rotation

More offset =more shearing

Cone offset□

Cone geometry

Teeth: long, slender, widely-spaced, mill tooth or tungsten carbide□Cone geometry: High cone effect□Bit operation: High RPM, low FOB□Drilling Action: Shearing□

Low compressive strength, plastic formations

Teeth: Numerous, closely spaced, short, blunt teeth, tungsten carbide□Cone geometry: Little to no offset□Bit operation: High FOB, low RPM□Drilling Action: Crushing□

High Compressive Strength, Brittle, Abrasive Formations

Allow cones to rotate

Support thrust loads

Function○

Not sealed - Lubricated by drill fluid and susceptible to grit of drill cuttings□Used on cheap, inexpensive bits□

Ball & roller

Not susceptible to grit from drill cuttings□Much more expensive than non-sealed bearings□

Sealed & Lubricated

Last longer□

When the bearing wears out before the bit, the cones can fall off and fall to the bottom of the borehole and then must be 'fished' out

Developed with the advent of tungsten carbide bits. Bearings would wear out before the bit itself (prior to advent of the journal bearing)

□

Journal Bearings

Bearing Types○

Bearings-

Threaded connection○

Bearing pins○

Lubricant reservoir○

Jets (nozzles)○

Bit Body-

Maximize ROP

Maximize depth drilled

Maintain hole gauge

Objectives○

With a lesser ROP, the less time is spent tripping the bit due to wearing bits

The deeper drilled, the less important ROP becomes○

Bit Selection-

International Association of Drilling Contractors○

Used as a means to standardize rock bit design○

Series (cone offset)

Type (Tooth length, spacing)

Gauge protection□Bearings□

Features

Three digit code to assist in rock bit selection for drilling in various formation types○

IADC Rock Bit Coding System-

Amount of cutting structure gone□T = Tooth wear in 1/8th's

A three digit code○

Bit Evaluation-

Drilling and Wells

Drilling and Wells

Amount of cutting structure gone□B = estimate of the amount of bearing life used (1/8th's)

G = inches undergauged

First Digit:-

1, 2, and 3 designate STEEL TOOTH BITS with 1 for soft, 2 for medium and 3 for hard formations.

4, 5, 6, 7 and 8 designate TUNGSTEN CARBIDE INSERT BITS for varying formation hardness with 4 being the softest and 8 the hardest.

Second Digit:-

1, 2, 3 and 4 are further breakdown of formation with 1 being the softest and 4 the hardest.

Third Digit:-

This digit will classify the bit according to bearing/seal type - see information on different bearing types - and special gauge wear protection as follows:

Standard open bearing roller bit1.Standard open bearing roller bit, air-cooled2.Standard open bearing roller bit with gauge protection which is defined as carbide inserts in the heel of the cone

3.

Sealed roller bearing bit4.Sealed roller bearing bit with gauge protection5.Journal sealed bearing bit6.Journal sealed bearing bit with gauge protection7.

Drilling and Wells

Drilling and Wells

Drilling method○

Bit selection and operation○

Drilling fluid selection○

Drilling fluid control○

Manipulating how drilling fluid goes through the system

Drilling fluid hydraulics○

A number of controllable factors affect drilling economics-

Drilling fluids are key to drilling optimization and to the success of drilling operations-

Types of Drilling Fluids-

Less chip hold down which results in the bit not having to re-grind bedrock material

Drilling with a negative pressure differential between the formation & borehole

Fast ROP□

Measure water coming to the surface

Easy to identify water-bearing zones□

Drill solids have less of a chance of plugging off the porosity & permeability of the formation

Less damage to producing zones□

Advantages in consolidated rock where low quantities of water are encountered

Drilling in overburden

Hydrostatic pore pressure increases the tendency of the borehole to collapse

Unstable boreholes□

Little control over formation water□

Limitations

Air Based○

A suspension of bentonite clay or polymer in water

Control of unstable formations

Control of formation water

Down hole pressure control□Advantages

Reduced ROP in consolidated rock□

No idea what the water producing zones are producing

Water bearing zones are smothered□

Drilling fluid plugging off formation fractures with drill solids

Producing zone damage□

Limitations

Water Based○

Bentonite Drilling Fluids-

Most widely used water-based drilling fluid○

For cutting removal□

As fluid rises from the bottom to the top of the borehole velocity decreases and viscosity increases through each section

◊

Thixotropic gel structure

Suspended cuttings when circulation is stopped□

Viscosity and gel strength

Important properties to control:○

Drilling FluidsOctober 17, 2015 9:30 PM

Drilling and Wells

Drilling fluid hydraulics control□

Formation permeability◊

Overbalance in pressure◊

Two things required:

An impervious filter cake is required□

To protect the producing zone and improve well development□

Water loss/filtration control

To stabilize boreholes and control formation pressures□Maximize ROP□

Mud density control

Bentonite clay is important in all of these areas of control○

Bentonite Drilling Fluids Solids Fraction-

Liquid Fraction

Solids Fraction

Bentonite drilling fluids have two components○

Properties of bentonite drilling fluids are largely a function of the solids fraction○

Two groups of Solids-

Non-reactive

Reactive

Low Gravity○

Barium sulfide □Weighting agent□

Non-reactive (barite)

High Gravity○

Don't respond to a changing chemical environment

Particle density 2.2-2.7 g/cc□Bulk density - Porosity□

Made up of drilled solids:

Low Gravity, non-reactive solids:○

Drilling and Wells

Bulk density - Porosity□Sandstones (Bulk Density) / Sand (Particle Density)□Siltstone (Bulk Density) / Silt (Particle Density)□Limestone□Some shales / Clays□Crystalline rocks□

Higher frictional effects□Higher pump pressures (due to resistance to flow)□

Slow rate of penetration

If density = greater than formation pressure & you encounter porosity & permeability

◊

Lost circulation

Density□

Excessive viscosity and density

If drill solids stay in drill fluids, then you aren't getting representative samples

You want discreet samples from a known depth interval□Poor sampling

Fluid loss□

Solids plugging off porosity

Formation damage□

Fix by lowering pressure & allowing formation pressure to exceed drilling fluid pressure

◊

You won't be able to pull the drill string out of the hole due to frictional effects

Permeability□

Thick, permeable filter cakes and formation damage

Grit can damage borehole & drill pipe□Abrasive

Shale shaker□Sedimentation□Desander/Desilter□

Worst case scenario

Drill fluids are expensive and dumping them is last case scenario

Add water to dilute□

Their concentration is lessened using solids control procedures

Low Gravity, non-reactive solids exert a poor influence on fluid properties○

Respond to a changing chemical environment

Bentonite□

Prevents heaving of the shales by inhibiting the mud

Counteracted by adding KCl–

Chunks of the shale will fall (heaving) into the borehole due to expansion

Drilling through sodium montmorillonite clay/shale, there will be a large hydration potential

Can have salinity, Osmotic, effects draw the water in your drill fluid into the formation

◊

Can cause drilling problems

Some 'native' shales & clays□

Consist of:

Drilling fluid properties are controlled in large part by manipulating bentonite behaviour

Reactive, low gravity solids○

Colloid: (0.001-2Microns) Extremely small, insoluble material that can remain in suspension

◊

Colloidal (~0.001 - 2 microns diameter) with a plate-like structure

Provides a very large surface area/mass ratio

Water vibrations can keep these particles in suspension◊

Molecular bombardment contributes to particle suspension

Extremely small particle size□

Like charges repel to break down clay aggregates and disperse particlesUnbalanced (negative) surface charges□

Reasons:

Bentonite's use as a drilling fluid additive is because it can form a stable, viscous suspension○

Drilling and Wells

Want individual particles and not aggregates ◊

Like charges repel to break down clay aggregates and disperse particles

Helps wedge particles apart ◊

Hydration separates (disperses) clay particles to help break down aggregates

Extremely high hydration potential□

Contributes to clay dispersion

Mixing or pumping allows for clay dispersion

Susceptibility to shearing forces□

Unstable suspension: colloidal, building up a mass and falling out of suspension

If insufficient, particles will adhere when they collide and settle out resulting in an unstable suspension

□Electrical and hydration forces are modified to control drilling fluid behaviour

True commercial clay

2:1 layer alumino-silicate

Bentonite□Smectites (Na and Ca montmorillonite)

Kandites

Illite

Chlorite

Clays are a small group of minerals, the most important members being:○

All are hydrous alumino-silicate minerals

All have a layered structure of alternating sheets of silica and alumina

Occur as extremely small, thin, plate-like particles

The chemical makeup and structure of these clays are similar○

Drilling bentonite is sodium montmorillonite ○

Bentonite Clay Structure and Chemistry-

Sodium Montmorillonite (Bentonite)-

An alumina sheet is sandwiched between 2 silica sheets to form the clay layer

Silica sheets face each other across adjacent layers

2:1 layer Al-silicate clays○

Significant isomorphous substitution occurs in the crystal lattice structure○

In addition to the +/- charges at the edges of the layers from exposed atoms

Substitutions impose a net negative charge on the face of the colloid layer○

Serves to link adjacent particles face to face rather loosely

The negative static surface results in the occurrence of a cation cloud in the interlayer space○

In sodium montmorillonite the dominant cation in the cloud is sodium at 60 -70%○

The cations are adsorbed rather weakly by electrostatic attraction

This allows cation exchange to occur driven by mass action effects

Cations in the cloud are exchangeable with those in the surrounding solution○

Smaller the ion the greater tendency for adsorption□Cation size

Ex.

Higher the charge the greater tendency for adsorption□Cation charge

Increase concentration high enough and it will counteract any effects of charge & size□Concentration in solution vs. that adsorbed (mass action)

Cation exchange is a reversible reaction that is controlled by○

When bentonite is exposed to water, strong hydration forces pry apart individual layers○

Unbalanced, negative surface charges

Mechanical shearing forces if the fluid is mixed or pumped

Particle separation is further enhanced by:○

Particle separation (dispersion) by hydration, electrical and shear forces contributes to the development of a stable, viscous suspension

○

Results in greater frictional resistance to flow

Higher viscosity results from higher total particle surface area and less available "free" water○

Bentonite Clay Particle Arrangement -

Drilling and Wells

Water hydration - water is not free to flow, causing an increase in viscosity

Water becomes tightly bound □Results in greater frictional resistance to flow

Affects the electrical force field and the degree of hydration

The degree to which dispersion occurs depends on the type & amount of cations in the cloud

The degree to which dispersion occurs depends on the type and amount of cations in the interlayer cation cloud

○

Particle arrangement in the non-hydrated state□Can be caused by excess flocculating cations ( in solution□

Decreased number of discrete particles present

Reduction in total particle surface area

Less water bound up, less resistance to flow = less viscosity◊

Partial dehydration of clay surfaces

Results in low fluid viscosity:□

Face-face arrangement:

Aggregated State○

Complete separation of particles

Result of hydration, electrical and shear forces

More discrete particles□Greater total particle surface area□More area for hydration□

Causes flocculation of particles

Positive charges on exposed sides□

Contributes to higher viscosity compared to aggregate state

Dispersed State○

Edge-edge, edge-face arrangement

Result: a dramatic increase in viscosity

Creates gel structure

Reduction in electrical repelling and hydration forces (flocculating cations)□

Allows particles to come together in closer proximity

Crowding of particles□

Thixotropic Properties: manner by which fluid thickens when shearing or mixing is reduced

Decreasing shear/mechanical forces□

Caused by:

Flocculated State○

Dispersion of particles that were once flocculated

Water softening agent

Sodium Acid Phosphate □

Phosphate can render positive end charges useless by binding to them, causing further deflocculation

Removing calcium will deflocculate the mud□

Works better at increased pH□

□

Role of mud thinners (SAPP = )

Deflocculated State○

Particle Arrangements-

Drilling and Wells

Viscosity is measured routinely using a Marsh Funnel

Useful to determine if viscosity has changed

Fine Sand: 35-45 s/L□Medium Sand: 45-55 s/L□Coarse Sand: 55-65 s/L□Gravel: 65-75 s/L□

O.K. to determine if viscosity is in the proper range in arbitrary, relative terms (s/L or s/qt)

Marsh Funnel○

Torque generated by the fluid between the spinning cup and the 'bob'

As torque increases, the 'bob' will spin to stabilize and give you a reading

Fann Viscometer○

Viscosity and Gel Strength Control-

Drilling and Wells

Fluid Viscosity (mPas)□

Plastic Viscosity: That part of overall viscosity due to mechanical friction effects◊

Shale shaker - change to a finer screen–

Desander/desilter –

Worst case scenario dilute with water–

Perform solids control procedures

High PV = Treat the fluid mechanically to reduce non-reactive solids (drill solids)◊

Run at 600 RPM and take a reading. Then run at 300 RPM and take a reading. Perform calculation.

–

Determined by:◊

Plastic Viscosity (PV)

That part of overall viscosity due to electrical friction effects of bentonite◊

Determined by:◊

High yield point means high flocculating tendencies◊

Yield Point (YP)

Reasons for abnormal viscosity□

Listed above in YP & PV

Best treatment for abnormal viscosity□

YP = conditions of flow◊

Measure of electrostatic attraction of bentonite particles @ static conditions (under no flow)

The reading = energy required to be applied to overcome gel strength◊

10 second reading @ 3RPM, 10 min reading @ 3RPM

Gel Strength□

Determined by equations that tell you which flow conditions are occurring◊

Fluid layers flowing past one another in an orderly fashion–

Results in a parabolic velocity flow profile in cylindrical pipes

Laminar Flow Regime: Orderly flow fashion @ lower flow velocities in which layers flow past one another.

◊

Laminar vs. turbulent flow

Fluid Hydraulics□

Offers more meaningful data including:

Drilling and Wells

Velocity in the center of the pipe is the same as the velocity on the edges of the pipe

Turbulent Flow Regime: Chaotic flow pattern at higher flow velocities in which case frictional shear at the fluid layer interfaces causes orderly laminated structure to break down. Results in a flat velocity profile in pipes.

◊

Can be calculated◊

(Friction) pressure losses in the flow system

Lowers flocculating tendencies◊

Higher corrosion control◊

Facilitates precipitation of

Drilling Mud Treatment□

Drilling and Wells

Treating drilling mud is usually done with Caustic soda, hydrated lime, & soda ash

However, if you have flocculating bentonite they cannot move into the pore spaces which results in thick permeable filter cakes

◊

Dispersed bentonite creates a thin impermeable filter cake

With an elevated pH it dissociates into

SAPP - ◊

NaOH

IAP = Product of the activities of reaction products–

Saturation index =

If SI = Greater than 1 = 1 Supersaturated causing precipitation of mineral

If SI = Balanced = Neither precipitation of mineral or dissolving of mineral

If SI = Less than 1 = 1 Solution is under saturated causing the mineral to dissolve

Elevating by deprotonation of meaning the IAP will be greater

than 1 causing Calcite to precipitate out.–

Caustic Soda◊

Raises pH

Converts alkalinity into favourable forms

Conversion of

@ high pH–

Calcium is added, which is the ion we want to precipitate out

Common ion effect–

Two things are happening:

Increases carbonate, facilitating precipitation of –

Hydrated Lime◊

Lime removes carbonate hardness

Soda removed non-carbonate hardness

Lime-Soda Softener◊

Common Treatment Options:

The study of the deformation and flow of material in response to an applied stress○

For fluids: this means taking certain measurements on the fluid, the results of which are used to predict flow characteristics under different conditions

○

Orderly, laminated flow structure at lower flow velocities□Laminar Flow

Chaotic flow behaviour at higher flow velocities□Turbulent Flow

Terminology Related to Flow:○

Critical Velocity

Rheology -

Drilling and Wells

Critical velocity is often not a point. There is a transitional flow.□

Transitional Flow

□

Flow velocity below which flow is laminar and above which flow is turbulent

Critical Velocity○

Pressure on a fluid that is lost by frictional effects as it flows from one point to another in a flow system

Friction Pressure Loss○

The internal resistance to flow from the friction force of fluid layers sliding past one another

Measure of torque (rotational force) for a given RPM□

Dynes =

Units: □

Dial reading * 3.406 = □

Indicated by the dial reading (deflection units) on the Fann Viscometer

Shear Stress○

The velocity at which one layer slides past another at some known distance

Speed with which outside layer moves in relation to the stationary layer next to the bob□On the Fann viscometer: this is the distance from the outer layer to the stationary layer at the bob

□

Units: reciprocal seconds

Fann viscometer: RPM * 1.703 =

Shear Rate○

The relationship between shear stress to shear rate defines how a fluid flows and defines fluid viscosity

Viscosity○

Drilling and Wells

viscosity

More commonly: centipoise = mPa

Models of Fluid Flow-

Eg. Water□Describes the flow behaviour of Newtonian = true = proper fluids

Shear stress & shear rate are constant in Laminar Flow□The relationship between shear stress and shear rate is constant under conditions of laminar flow

□The Newtonian Model

Newtonian Model○

For a Newtonian fluid and the Fann viscometer□

Plastic viscosity

Inert solids increase mechanical friction□

Contributes to YP

Bentonite increases electrical (& mechanical) friction□

The presence of suspended solids in a fluid increases frictional resistance to flow (shear stress), hence viscosity

The velocity profile in pipes is affected (flattened)□Bentonite causes non-Newtonian behaviour

The SS/SR ratio decreases with increasing shear rateThe shear stress/shear rate ratio is not constant under conditions of laminar flow□

Non-Newtonian Fluids○

Drilling and Wells

Ie. The fluid shears thin such that viscosity lessens with increasing shear rate under conditions of laminar flow

◊

The SS/SR ratio decreases with increasing shear rate

This is shear stress/shear rate ratio for a given shear rate

Bentonite fluids (& other non-Newtonian fluids) have an "effective" viscosity for a given shear rate

□

= Effective Viscosity◊

For a non-Newtonian fluid and the Fann viscometer:□

Also non-Newtonian as well

Needle shaped, causing more interference causing more viscosity□Example of a shear thickening fluid is Attapulgite clay

Shear Thickening Fluids○

Ie. Some definite force has to be applied to initiate flow after which there is a constant rate of increase in shear stress with increasing shear rate

Bentonite fluids behave in a plastic fashion○

□ □

□

□

□

□

From the Fann Viscometer:

Bingham Model○

Bingham (Plastic) Model of Fluid Flow-

Physical & Chemical Properties of Polymer as a Drilling Fluid Additive-

Drilling and Wells

Guar plant extract

Ex. Revert□

Less than mineral particles

Smaller size than bentonite

Resistant to molecular bombardment (of water)

Has a low SG□

A long chain, coiled, colloidal, organic compound of high molecular weight

Polymer is used as a drilling fluid viscosifier○

Low SG and small size keep it in suspension□The tangled mass creates mechanical friction shear stress (viscosity) under flow□

A stable, viscous suspension forms

When added to water, a tangled mass of particles develops○

It takes ~1/10 as much polymer by weight as bentonite to build comparable viscosities○

Can drill through gypsum without many issues

No negative face charges or +/- end charges □Polymer is less susceptible to flocculating cations compared to bentonite

Polymer fluids have no YP or gel strength

Bentonite = suspension weighting: Barite□Polymer = Solution weighting: Soluble Salts□Sodium chloride, NaCl; or Calcium Chloride □

Polymer fluids are weighted using soluble salts

The surface of these particles is non-charged (non-ionic)○

Less particle interference = less frictional resistance (shear stress)□At higher shear rates the tangled polymer particles stretch out and slip past one another more easily

Polymer forms shear-thinning drilling fluids○

Polymer fluids are low solids, clay-free fluids without a gel strength○

No gel structure

Cuttings drop out easily at surface□

Cuttings drop out readily at surface

Better density control because of better solids control□

Better solids control

20 mPa s bentonite fluid ^8.65 ppg

20 mPa s polymer fluid ^8.2 ppg

Less solids at lower SG to build a given viscosity □Faster ROP

PV = mechanical effects

Because of PV = better solids control□

No flocculating tendency in polymer fluid

Because of YP = No charged particles□

Better viscosity control

Material sample is more accurate due to less re-circulation of cuttings

Better solids control□Better formation sampling

Better solids control helps keep grit out of the piston pumps□Less pump wear

Small tiny particles plug off the smallest of pore spaces

With flocculated particles, mass of particles, the filter cake is less efficient ◊

No flocculating of particles

Formation of thin, tough, impermeable filter cakes□Good fluid loss control

Breaks down naturally or through the chlorination process (caused by oxidization)◊

The polymer is organic and breaks down readily

Better fluid loss control due to less formation damage□Better well development

Less demand on pumps◊

Lower friction pressure loss

Shear thinning nature□Good hydraulics

Advantages to use of polymer fluids:○

Drilling and Wells

Less demand on pumps◊

Hole deviation can wear the drill pipe down

High lubricity (slippery)□Lower rotational torque and wear on pipe

Describes the flow behaviour of fluids that behave in a pseudo-plastic fashion such as polymer drilling fluids○

K = Consistency index

N = Power index

○

N = 1 for Newtonian fluids

The power index indicates the degree of non-Newtonian behaviour and how shear thinning the fluid is○

The consistency index is the shear stress (dynes/ ) at a shear rate of 1 ○

As a fluid becomes more viscous, K increases○

As a fluid becomes more shear thinning, n decreases○

Polymer and/or Bentonite

Both n and K values are a function of the viscosifier ○

N = tangent of the slope on a log - log plot of shear stress vs. shear rate

K = the intercept of the slope with the shear stress axis

Values of n and K are shear rate dependent ○

Power Law Model of Fluid Flow-

Plug flow = plug of a fluid initially moving through a pipe○

○

○

○

○

○

Water = 0.001

○

Turbulence is predicted for a Reynolds Number greater than 2100○

Ex.

□

□

V = 0.021 m/s□

Example for water in a 0.1m diameter pipe

Transitional Turbulence is from a Reynold's number between 2100-4000○

Reynolds Number-

□

V = 0.04 m/s□

□

V = 0.0105 m/s□

Example for water in a 0.2m diameter pipe

□

V = 0.02 m/s□At higher p (fluid density), higher D (diameter) = lower Critical Velocity to transition to turbulent flow

At higher = Higher critical velocity required to transition to turbulent flow

N = 0.6□Example of lab fluid containing bentonite:

Drilling and Wells

N = 0.6□P = 1036 □ □D = 0.1□

3470-1370(0.6) = 2648□

□

V = 0.51 m/s□It would take speeds in excess of 0.51m/s to induce turbulent flow□

Critical velocity = velocity that will take one from laminar to turbulent flow◊

Velocity required to create turbulent flow

This results in high dispersive effects in the water mass◊

In turbulent flow the pattern of flow is not straight

Use of the Reynolds number looked at in terms of a pipe○

Fluid effective viscosity & density ○

Roughness of the surface◊

Friction factor◊

Kind of material (PVC, cast iron, steel)

Flow configuration (diameter, bends, elbows, valves)○

Laminar vs. Turbulent Flow-

Drilling and Wells

Well drilling technology○

Well completion and development technology○

Well maintenance and rehabilitation technology○

There are three areas of water well technology regarding the design, construction, maintenance and long term integrity of water wells:

-

There are similar considerations in monitoring well construction-

Safe from arsenic, uranium, radon□

Coliform bacteria testing

Sanitary□

To maximize well yield and long term hydraulic efficiency of an aesthetically pleasing, safe, sanitary water supply

Objective○

Water Well-

Hydraulic efficiency is not a concern□The ability to measure water levels accurately□

To obtain accurate water level measurements

To retrieve representative water samples from a known depth interval

Objectives○

Monitoring Well-

Domestic

Municipal & Industrial

Water well□

Monitoring Well□

Done to allow you to evaluate groundwater resources

Test well□

Denser than water

Town of Amherst drilled test wells to test for the presence in the water

□

Can travel long distances throughout the area□

DNAPL - Dense non-aqueous phase liquid

DNR have a network of monitoring wells□

T - Ability of the aquifer to transmit water

S - How much water can be used in an aquifer

Can determine aquifer transmissivity & storativity □

Monitoring water levels

Observation□

Purpose of well

Topography

Water table/potentiometric surface

Eg. Slope gradients□Make use of existing hydrogeologic conditions

Eg. Up gradient of septic fields□Locate wells up gradient of nearby potential pollution surfaces

Large vs smaller drilling rigs

Size of work area□Easy access for rehabilitation

Water protection issues□Location

Formation characteristics □Hydrogeological setting

Drilling methods chosen and procedures followed are affected by○

Well drilling technology-

Water Well TechnologyTuesday, November 03, 2015 1:19 PM

Drilling and Wells

Alluvial - Sands & gravels□

An air drilling collapse–

Cohesive is less prone to collapse and can be drilled with air

Loose or cohesive–

Above two examples can contribute to hole collapse

Till - Clay to boulders□

Sediments

Sedimentary □

Igneous

Metamorphic

Crystal□

If the above two examples are fractured it will increase chances of lost circulation and what type of bit will be selected

□

Bedrock

Formation characteristics □

Loose material = water is preferred

Consolidated = air is preferred

Influences water vs air drilling□How much loose material vs consolidated

Depth to bedrock□

Air based vs water based□Pressure control

Depth to water table□

Pressure issues□Down hole pressure control is a concerns□

Confined Aquifers

Confined vs. unconfined aquifers□

Allows you to make accurate pore pressure

Distance to confining layer and potentiometric level□

Advantage of drilling with air is lost with lots of water

Drilling through gypsum bed can affect the use of bentonite vs polymer

□Water quality

Groundwater quantity and quality with depth□

Methods for drilling wide diameter vs small diameter (Hoisting power is a factor as well)

□

May have to drill a tapered hole with deep wells□

Well depth and diameter

Metamorphic/igneous can be fractured pieces□Well screen analysis□

Sampling requirements

The choice of air, mud, or polymer□

Can't be hard water with the use of bentonite

Disinfected; if not you will contaminate the well

When drilling with an air based fluid, the mist water will be chlorinated

pH & TDS are a factor

Quantity and quality of the mix water□

Drilling fluid system

Crystalline rock - down hole hammer

Bit will dictate rig used□Drill bit selection

Required yield dictates the pump choice which dictates the casing requirements. In order to fit a pump down the well column the diameter must fit the casing diameter.

□Casing and screen installation requirements

Grout requirements

Drilling and Wells

Used in combination with casing to protect the well intake from surface & subsurface contaminations

□

Ie. Lost circulation or collapsing formations

Can be used in combination because it can isolate problem zones□

Material - Bentonite vs Cement□Methods of installation□

Greater diameter borehole than the well casing to accommodate grouting

Dictates well diameter□

Grout requirements

Availability of equipment

Cost

Trained operators

Well construction regulations of the NS Environment Act□Regulations

Applied between the end of the drilling phase and start of production○

Pumps wear out quickly□Turbidity free water□

To produce sediment free water

Decreases the friction loss and increases the well efficiency□Increase hydraulic efficiency at the well intake

Two reasons for developing a well○

Well completion and Development Technology-

Consolidated bedrock

Relying on the occurrence of fractures that will produce water

Open hole□

Formation material is coarse grained and with a wide size distribution you can naturally develop a well

□

40% retained size is selected for the screen slot size □

Natural development

If material is uniform like a sand□Filter pack should be uniform, rounded, clean, quartz (sand)□Allows for high porosity & high hydraulic conductivity□

Filter packed

Screened□

Interval

Diameter

Slow size (based on sieve analysis)

Material - stainless steel

Can collapse the screen while developing the well□Collapse strength

The well is then developed

After developing the well, it is then grouted

Casing is driven into the unconsolidated material layer, sandy layers, then the bailer gets a representative sample allowing the proper well screen gauge size. Once the screen is selected it is telescoped in and the casing is then pulled back up to the top of the sandy layer.

□Pull back method for screen installation

Well screen design and installation□

Filter pack design and installation□Casing design and installation□Grout□Well development□

Well intake

Considerations○

Drilling and Wells

Accomplished by placing a surge block inside the casing; once it becomes easier to force the surge block up and down in the well casing you can place it inside the well (below the borehole)

□Surging

Provides back and forth energy pulling water in and out of the well

□Swabbing

Nozzles pump high velocity energy at the well intake□Jetting

Works like jetting□Compressed Air

Not the best way to develop a well because of a couple of reasons. The first reason is that water only moves in one direction. The second reason is that the grit from the development of the well will chew up the pump.

□Over Pumping

Well development□

Working on the aquifer material further away from the well (as opposed to well development in the vicinity around the well)

Freezes the water in the well and outside the well

Dry ice □

HCL - to remove the carbonate mineralization like calcite cement which can be removed. Increases the porosity in the formation

Acid □

Bedrock wells (never done in unconsolidated sediments)Hydrofracturing□

Techniques:

Aquifer stimulation□

Drilling and Wells

Bedrock wells (never done in unconsolidated sediments)

Focuses on fractures that are already there

Sand gets blown into the formation acting as a prop

Not used very much anymore (less common)

Blasting□

Drilling method, location, construction details, lithology log, drilling company/driller, well yield, & client

CMHC requirement□

Well log database - civic address & owner of the property at the time of the well drilling operation

Drilled well report must be admitted to the department of environment

Dart valve bailer (cable tool)□Measure draw down in the well□

Required bail down test of 1 hour duration

Blow down air and measure the amount of water that comes out of the well

□Air lift pump test of at least 1 hour duration

If no rig is on site, you perform a pump test for a 6 hour duration. Then, measure the draw down and rate of recovery.

For an anticipated well yield <23,000 L/day

Must perform a pump test of at least 24 hours

Draw down & recovery are measured

For an anticipated yield greater than 23,000 L/day

Well yield determination□

Based on well yield and total dynamic head requirements (lift requirements)

Pump selection□

Ex. Keep the well up gradient from nearby contaminant sources; ie. Septic systems

Make use of existing hydrogeologic setting

Must be screened to keep out pests like earwigs, mice, & squirrels

□Well cap with compression seal & air vent of adequate size

Must have a well cap that is 6 inches above the ground surface

Makes use of the pitless adapter system

Well head protection□

Performed for quality assurance purposes

Checks the drawdown of the well

Maintenance○

Rehabilitation

Well maintenance and rehabilitation technology-

Drilling and Wells

Ie. Drawdown is not what it used to be□Performed in response to reduced water quality or well performance

Rehabilitation○

Advantage of using grout is it provides a protective sheathing□Corrosion - steel casing exposed to soils

Water will have a rusty brown colour & turbid water

6" in diameter - well casing of this size is for this purpose

Install a liner and grout around it

Direct flow of surface water through a fracture□Casing set too high

Casing○

Voids/gaps in the grout

Grout○

Collapse or suffer sand abrasion (open slots and pumps sand)

Well screen○

Drawdown is the difference in static water level + the pumping water level□

Well performance is measured in terms of well specific capacity = well yield (pump rate) drawdown inside the well

With increasing pumping time, the wells specific capacity will decrease

Pump○

Cycling on/off of the pump can cause turbulence, causing the migration of particles towards the well intake

Short circuiting the hydrologic cycle which can increase migration of particles toward the well intake as cementing agents dissolve

□

Silica

Calcite

Two major cementing agents

Water can be under-saturated due to short-circuiting□

If this happens it is cause for re-development of the well □

Change in water chemistry @ pumping conditions

Physical plugging of the well intake○

Iron bacteria, oxidizing Fe for energy

Buildup of a slimy biomass which plugs off the well intake causing a reduction of well specific capacity

Kills off bacteria□Oxidizes the slimy biomass □

Treatment is Shock Chlorination

Biological plugging of the well intake○

Calcite - □Dolomite - □

Commonly a carbonate scale

Presence of carbonic acids readily dissolve carbonates

Well intake incrustation ○

Water moves from an area of high pressure to low pressure□Results in degassing causing the a reduction of being produced□Causes mass action effects □ □ □

□

□Mass action effects move to the product size causing the formation of carbonate scaling

□

In an unconfined aquifer

Drilling and Wells

carbonate scaling

Same reaction occurs as in an unconfined aquifer□Water moved from high PE to low PE□

In a confined aquifer

Acids commonly used are HCL, sulfamic, & phosphoric □Requires acid treatment

Drilling and Wells

Direct (Circulation) Hydraulic Rotary Method-

Fast ROP in a wide variety of formation types

Capable of great depths

Much technical information

Causes placement of the well casing and grout to be difficult

Results in hole deviation□Rig must be kept level throughout the drilling job

Effective○

Advantages Disadvantages

Penetration rates are relatively high in all types of materials

Drilling rigs require a high level of maintenance

Minimal casing is required during the drilling operation

Mobility of the rigs can be limited

Rig mobilization & demobilization are rapid Most rigs must be handled by a crew of at least two people

Well screens can be set easily as part of the casing installation

Collection of accurate samples requires special procedures

Use of drilling fluids can cause plugging of certain formations

The drilling method is difficult and less economical in extremely cold temperatures

Drilling fluid management requires additional knowledge and experience

Advantages and disadvantages (pg 278)○

Air Rotary Drilling-

Borehole pressure under formation pressure

Less chip-hold down□Very good flushing from the bit□

Fast rates of penetration

Direct rotary with rock bits

Down-hole hammer

Underbalanced drilling○

Advantages & Disadvantages (pg 279)○


Cuttings removal is extremely rapid Restricted to use in semi-consolidated and well-consolidated materials

Aquifer is not plugged with drilling fluids

High fuel cost-

High initial cost and maintenance costs of large air compressors

Mud pumps are not used during air drilling, eliminating that maintenance cost

Bit life is extended

Well Drilling TechnologyTuesday, November 03, 2015 6:11 PM

Drilling and Wells

Effects bearings with mud○

Drill fluid is less abrasive-

Bit life is extended

Drilling operations are not hampered by extremely cold weather

Penetration rates are high (especially when using down hole hammers) in highly resistant rocks such as dolomite or basalt

An estimate of the yield of a particular formation can be made during drilling

Casing Advancement Drilling Methods-

Hole stability of cable tool method□Speed of air rotary drilling□

Combine

Casing Drivers○

Can't use rotary table drilling

The casing driver is an independent, air-operated piston device in the mast of a tophead drive rig

○

In concert

Eliminated heaving in a borehole when below the water table□Gives good representative samples□

Drive casing ahead of the bit in unconsolidated formation, then drill out the plug

Drill ahead of the casing, then drive casing

Casing can be advanced while drilling○



Wells can be drilled in unconsolidated geologic materials

Additional cost of equipment

A borehole is fully stabilized during the entire drilling operation

Noise of operation (casing hammers are noisy)

Penetration rate can be rapid even in difficult conditions

Clays or sticky shales can reduce depth capacity

Lost-circulation problems are eliminated

Accurate formation and water samples can be obtained

Reverse Circulation Methods-

Drilling fluid flow: down the annulus, through the bit, up inside the drill stem, through a centrifugal pump, into surface pits, flow by gravity to the annulus

○

Add polymer if necessary

Drilling fluid is muddy water○

High annular velocity

High fluid viscosity

Hole cleaning does not require○

20 inches, up to 60 inches

Effective in drilling large diameter filter packed wells in unconsolidated formations○

Drilling and Wells

High torques with large diameter rock and drag bits□Only table drive units

High capacity centrifugal pumps

Large diameter (8") threaded and coupled pipe

Air lift assist can be used to bypass the pump

Best with lower water tables

Keep hole full at all times□Fluid losses can be high

Setup○


Advantages- Disadvantages

Porosity & permeability of the formation near the borehole are relatively undisturbed (as compared to other methods)

Large water supply generally is needed during drilling

Large-diameter holes can be drilled quickly & economically

Reverse rotary rigs & components usually are larger and more expensive

Casing is not required during the drilling operation

Large mud pits are required

Well screens can be set easily as part of the casing installation

Some drill sites are inaccessible because of the size of the rig

Most geologic formations can be drilled (except igneous & metamorphic rocks)

For efficient operation, a larger crew generally is required as compared to that needed for other drilling methods

Little opportunity exists for washouts in the borehole because of the low velocity of the drilling fluid

Extra costs for drill pipe, special swivel, and air compressor (if the rig is not equipped with one)

Large-diameter boreholes can be drilled Drill pipe handling time can increase for deep holes

Penetration rates are high in unconsolidated sediments

Less drilling-fluid additive is required to lift the cuttings

Reduced development time

Once you get to a sufficient depth you can use air lift assist.

Air Lift Assist○

Drilling and Wells

Once you get to a sufficient depth you can use air lift assist.

Pump can be turned off and the rapid expansion of air will carry drill cutting to the surface

Without sufficient depth, you do not have sufficient expansion

Keeps a borehole pressure above formation pressure

Pressure differential can be maintained in low water table

Best with lower water table○

Usually a 24 hour operation□Keep borehole full at all times

Need large surface pit in order to provide water to the borehole at all times

As drilling proceeds, more fluid must be added to replace the cuttings being removed

Fluid losses can be high○

Double wall pipe, injecting air into the drill stem, pumping is accomplished via air lift assist.

○

Inverse Drilling-

Advantages & Disadvantages (Pg 280)○

Fast ROP

Too large for igneous and metamorphic geology

Large diameter holes○

Hydrostatic head maintained in the borehole

Casing not required○

Hole washouts not a probable situation due to water movement being too slow○

Reverse Circulation Down-Hole Hammer (Pg 266)-

Water or air can be used as a flushing fluid○

Only portion open to the fluid is right at the bit○

Lag time is significantly less□Sampling is known to have come from a known depth

Commonly used with mineral exploration○

Advantages & Disadvantages (Pg 280)○

Dual Wall Air Rotary Drilling-

Percussive method

Wrench square - clamps attach here□

First digit: Strands, bundle of strands◊

Second digit: Wires per strand◊

Left lay: Counter clockwise◊

16x19 Left Lay

Provides for the large crack in the formation◊

Makes for a highly elastic cable

Wire rope - Manilla rope□

Tool guide is used when you are above ground□

Drill string (image on page 275)

16-48" stroke length□20-40 Cycles per minute

Cable tool drilling○

Non-Circulation Methods-

Drive clamp - fits around the drive wrench square

Driven into the bedrock□Makes a tight seal□

Drive shoe -

Used to pile drive head into the casing□Drive Head

Unsaturated zone - drill 4-5 feet, then drive casing to depth□Saturated zone - drive casing, then drill to depth (drill out plug)□

Keep bit and casing shoe in close proximity

Unconsolidated formations○

Driving Casing-

Drilling and Wells

Saturated zone - drive casing, then drill to depth (drill out plug)□

No need for casing

Consolidated Formation○

4-5 feet thick, you must use the dart valve bailer or it starts to impede progress○

On a separate hoisting system all together○

Utilizes a carbide button bit○

Dart Valve Bailer-

Pumps & compressors aren't on the right

Inexpensive & operational costs are less○

Called a bail down test

Bailing at any time○

Thicker casing is required for cable tool drilling

Disadvantages○

Normally pulled up with casing spear

Specialized equipment are casing jacks

Keeps welds from breaking on pieces of casing that are joined□Pulling up on the casing keeps the casing in compression & not in tension

Some geologic conditions make it difficult to retract long strings of casing without using special equipment

○


Fast ROP

Good Sampling

Unconsolidated formations only○

From top of hole (highly mixed)

Pull out and sample the cutter head

At depth in conjunction hollow stem augers□Samplers:

Sample collection:○

Large diameter cylinder with angled blades

Cutting action = rotary cut

Where there is poor bedrock water yields□Very much like dug wells

Can be up to 48" in diameter, 50-100 ft deep

Hydraulic feed mechanism

Works best in cohesive clays

Advantages and Disadvantages (pg 281)

Bucket Augers○

Earth Augers-

Drilling and Wells

Advantages and Disadvantages (pg 281)

Consists of flights welded to pipe or bar

One section□Post hole digger□14-24" diameter to a depth of 50ft□

Best in clay formations with some cohesive strength

No good in unconsolidated formations□

Single Flight:

5ft lengths, 4-24" diameter

Flights welded to pipe convey material to surface□

Lead flight has cutter head and pilot bit□Depth of ~100ft□

Not good in loose material below water table

Best in cohesive formations□

Continuous Flight (multiple sections)

Very commonly used□Continuous flights and a drill stem that is truly hollow□Center rod is connected to the plug□

Geotechnical holes

Monitoring wells

Mineral wells

Mineral exploration -> Good sampling

Water wells

Widely used:□

Little problem with caving formations

Can pull out center rod, plug, pilot bit and install your filter pack, ◊

Stem acts as temporary casing

Effective□

Hollow Stem Auger

Solid Stem Augers○

Drilling and Wells

Can pull out center rod, plug, pilot bit and install your filter pack, well screen, etc

◊

Conductive to unconsolidated material, free of cobbles & boulders

Hand or solid stem□Start with auger

Vast underground storage tank□Sparging points - bioremediation - bubbling in oxygen to speed up the bioremediation process

□

Application

Shallow wells

Not grouted

Poor water quality protection for potable water□

Improper abandonment can lead to aquifer contamination□

No well reports submitted

Installed at random by non-certified people□

Problems

Well Points○

Rocks like boulders stop drilling□Rotary drilling can encounter cobble which can't be lifted out of the drill hole

□

Cobble can cave in and get the drill stem stuck in the borehole □

Slow or stop drilling

Sticking of drill stem or casing

Deflect bit or casing causing hole deviation

Dent/rip casing

Common in glacial tills and coarse alluvial deposits○

Remove

Push to one side and isolate with casing

Install a cement plug to consolidate and drill out with a bit designed for high compressive strength formation

Solutions○

Blasting

Down hole hammer

Drill out with a bit designed for high compressive strength formation

Destroy○

Problems with Cobbles & Boulders-

Perfectly vertical□Plumb

Boreholes commonly deviate from plumbness and alignment○

Plumbness, Alignment, & Deviation-

Drilling and Wells

Perfectly vertical□

Straightness□Alignment

A borehole out of plumb but in alignment can happen

Biggest problem is crookedness

Large diameter pipe through sharp bends□Casing installation

Casing leans to one side□Solution is to use casing centralizers□

Grouting

Screen leans to one side□Use centralizers□

Filter pack installation

Engine is at the top of the drive shaft instead of in the well□Vertical Turbine pump setting

Can wear out the casing□Wear on drill string

Wear on casing

Sharp bends□Stuck drill stem

Borehole deviation can lead to many problems○

Borehole straightness is most important○

2/3 the well inside diameter (inches) per 100 feet of pump setting depth (AWWA)

1 degree per 50 feet (EPA)

Rules re deviation (drift) tolerance○

Critical for vertical turbine pump installation○

Deflect bits, casing□Boulders

Alternation of harder & softer formations

The formation on the right is hard, formation on the left is soft, the bit follows the path of least resistance

<45 degree, holes drill up dip□

>45 degree tend to drill down dip□

Inclined strata

Causes of well deviation○

Drilling and Wells

Drill collars□

Lack of stabilization

Stabilizers□

Poor bit stabilization

Increased compression of the drill bit□Insufficient stabilization; lessened with increasing stabilization□

Excessive FOB

If it is not perfectly straight it will deviate□Important to use casing clamps when welding casing pieces together□

Trueness of casing or drill pipe

Application of pull down can cause this shifting

Over drilling time the rig is constantly being shifted□Drilling rig off level

Increasing pendulum length and weight

Reducing FOB

Promoting the pendulum effect□

Drill collars and stabilizers

Providing suitable stabilization□

Keep the tool perfectly parallel with the drill stem

When the clock strikes it marks the disk with a mark and it will tell you how many degrees you are deviated

◊

Inside is a clock mechanism

Deviation Survey□

Gives a complete picture of how the borehole is deviating and the direction the borehole is going

Avoiding a doglegged borehole is important

Directional Technology□

Allow the Pendulum Effect to work□

Excessive deviation can be addressed by:

Borehole deviation can be determined while drilling using a 'deviation' tool○

Drilling and Wells

Allow the weight of the drill collar to tend toward vertical

Influenced by weight of pendulum & length of pendulum

Decreasing the number of stabilizers on the drill collar increases the length of the pendulum

◊

Coupled with decreasing the FOB the borehole will straighten itself out

◊

Having stabilizers on the drill collar will tend to keep the borehole going in the same direction

Allow the Pendulum Effect to work□

The borehole needs to become straight slowly in order to avoid having a dog legged borehole

Wheels keep the tool aligned with the borehole or casing□More common in water well drilling□

Inclinometers (degrees of drift)

Plumb bob is dropped into the well, a plate is put on the wireline which reads the inches of drift with depth

□Plumb bobs and dummies (inches of drift)

Drift can be determined at the end of well construction○

Drilling and Wells

Dummie is a 40' length of pipe that is lowered into the borehole. If there is trouble getting the length of pipe down the borehole, the pump won't go down either

□

A valuable source of information on the subsurface○

An integral part of wellsite supervision○

Fractures & faults in bedrock

Bedrock maps will give you an idea of these

Lineaments□

Good indication of where to place wells

Water table slopes with topography

Topography□

Geology, hydrogeology, structural/ tectonic, soil and topographical reports and maps

Pickup fracture trends□Vegetation can indicate fractures in the subsurface□

Air photos and remote sensing

Gives indication of subsurface horizons

Depth of water table

Sledge hammer to the steel plate and each geophone picks up the reflection/refraction of waves to the surface

◊

Hammer seismic gives the best results in a water well setting

Surface seismic□

Measures interval transit time of compression waves◊

Indicates formation porosity and density◊

Lowered into the borehole and raised slowly◊

Greater the porosity, the lower the density, the greater the transit time

◊

Acoustic log

Measures formation electrical conductivity for lithology and grain size analysis

◊

Greater the specific conductance the greater the porosity due to pore space water content

◊

Conductivity log

Measures electrical potential between the borehole fluids and formation fluids

◊

To study lithology and variations in water quality◊

Borehole fluids & formation fluids, measures voltage potential, ◊

Spontaneous Potential (SP) log

Borehole wireline logging□

Geophysical testing:

Used in conjunction with other information sources○

Formation Sampling While Drilling-

Drilling and Wells

Relative salinity effects specific conductance

Borehole fluids & formation fluids, measures voltage potential, is setup between the two, results from the anode & cathode

◊

Measures formation H atom content indicating water-saturated formation porosity and moisture content

◊

More porosity, the greater the H atom, the greater emission of neutrons

◊

Commonly used to determine soil porosity◊

Neutron log

Measures gamma radiation to study variations in lithology (clay and shale content)

◊

Clay & shale accumulate ◊

Gamma log

Measures formation resistivity to identify formation salinity in porous and permeable zones

◊

Greater salinity, lower resistivity ◊

Resistivity log

Measures borehole fluid temperature◊

Used in grouting, cement gives off heat as it cures and this is recorded with a temperature log. Cold spots = holes in the cement

◊

Temperature log

Well log database at DoE–

Offset information

Aquifer (pump) test information

Uses bowspring arms to measure borehole diameter◊

Will tell you exactly how much grout you will need to fill the space between casing & borehole

◊

Caliper log

All information sources complement one another□

One shot deal - no 'do-overs'

Incorrect, expensive decisions can be made is non-representative samples are collected

The only way to verify is to drill and collect representative samples□

This can dictate the drilling method used, procedures to follow and sampling requirements

The objectives of the drilling/sampling program must be clearly stated and known by all

□

Representative samples must be collected that meet program objectives□

Commonly, composite samples are collected at 5 foot intervals, mixed thoroughly and interpreted

□

Lithology Log - A description of the physical characteristics of a rock unit or a sedimentary unit

Results are presented and interpreted on a litholog□

For the same operating conditions ROP is a function of formation compressive strength

This can be applied to any drilling method

Bit bounce - rattling of rig mast

Rig chatter - occurs because of differential torque from encountering fractures & cobbles

◊

Engines go under greater strain due to increased torque

Engine tone increased torque; example is in sands◊

Note rig behaviour

Lost circulation◊

Note hole behaviour

Changing ROP can be correlated with variations in lithology□

Results are presented and interpreted on a litholog

Drilling and Wells

Lost circulation◊

Air drilling or cable tool method

Hole taking on water◊

Heaving formations◊

Tight formations◊

Well flows with pump off◊

Change in bit type

Change in bit diameter

Change in bit condition

Drilling fluid properties

Hydraulics (pump rates)

Document anything that may affect ROP and sample quality□

Keep in close touch with the driller□Feed the driller with copious amounts of Tim Hortons Coffee □

Mixing effect - causes non-representative samples

Large length can cause heavy particles to move slowly up the annular space

◊

Issue is that cuttings will be less likely to settle out at the surface and will recirculate into the borehole

This effect can be lessened with increased viscosity◊

Particle size separation (slip velocity)

Hole depth□

Silts and clays washed out into the drilling fluid & will be missed in the examination of the drilled cuttings

Washing of sands and gravels□

Hard to distinguish native clays from the bentonite clay

Polymer is better for this type of examination

Bentonite contamination□

Impedes settling out of sediments

Polymer gives a better sampling effect

Gel Strength□

Diamond bit - very fine sediment that is very difficult to distinguish

Drag, rock, hammer - Can have a wide size variety and easier to distinguish

Drag bit, rock bit, hammer bit, diamond bit◊

Influences sample quality

Bit type□

Problem in large or long open holes below the casing in unconsolidated material

Even in consolidated material you can have water sensitive shales that are very prone to heaving

Cavings□

Knowing all the information of the pump output is very important in determining this effectively

'Lag time' determination□

Widely used but has limitations re sampling

Collect composite samples at routine (5 foot) intervals□Mix and correlate with changing ROP□

Typically, sampling is done on a continuous basis

Eg. In response to drill breaks and rig and hole behaviour□Also specific depth intervals can be sampled

Stop drilling and rise drill string off bottom□Circulate the hole clean□Drill interval of interest (1foot-few feet)□

Steps:

Hydraulic Rotary Drilling○

Drilling Methods and Sampling Procedures-

Drilling and Wells

Drill interval of interest (1foot-few feet)□Stop drilling and circulate sample to surface□Correlate mixture with changing ROP through the interval□

Very costly option□Core sampling of consolidated rock is an option with direct rotary drilling

Results in less hole recirculation

Good solids control results in better sampling○

Drilled solids have no contact with the borehole wall

Minimal contamination from the open hole○

Turbulent flow in the drill pipe increases the lift capacity

Less slip velocity○

Reverse circulation rotary drilling-

Rock bits

Down-hole hammers

Suited for consolidated rock in which case problems associated with water based fluids are lessened

○

In consolidated rock you get nice clean samples

Poor sampling in unconsolidated formations○

Suited for high compressive strength, crystalline rocks (granites, basalts, metamorphics)

Aquifer storage and transmission of water is a function of fractures

Down-Hole Hammers○

Where fractures are the bit has an easier time moving through them□Increased ROP

Rig will bounce & shake when it encounters fractures from differential torque

□Rig chatter from differential torque

More (blast of dirty) water arriving at the surface□Hole behaviour

Drilling through fractures will produce cuttings that have weathering like iron staining (iron oxide staining)

□Look for weathering stains on cuttings

Calcite□Silica□

Look for fracture infilling

Fracture detection:○

Kitchen strainer on a pole for grab samples

Wire mesh sieve at the top of hole for composite samples of specific intervals

Sample collection○

Air Drilling Methods-

Driller uses cable feel and gravity free fall of the drill string to monitor down-hole conditions

○

Change ROP of the bit and casing

Changing water levels□

Ex. Confined aquifer situation - quicksand effect of pressurized sands & silts that make their way into the borehole

Heaving formations□

Hole behaviour

Monitor and record:○

No mixing/washing by a drilling fluid

No contamination from the open hole

No lag time

Representative samples from known depth intervals can be collected, especially in unconsolidated formations

○

Bail the hole□Unconsolidated formations

Procedure:○


Drilling and Wells

Bail the hole□Drive casing ahead of the bit through the interval of interest□Loosen plug with the bit□Bail□Thoroughly mix the slurry at surface□Correlate mixture with changing ROP (blows/foot) of casing□

Fast ROP

Good sampling

Widely used in unconsolidated formations○

From top of hole (highly mixed)

Pull out and sample the cutter head

At depth in conjunction hollow stem augers□

Gives you blows per foot.◊

Gives you porosity & density◊

Blow count - Number of blows it takes to get your sample.

Means more compaction of sample◊

Driving force requires thick walls

2"OD, I 3/8" ID, 1-2 ft long

A 'standard penetration test" is performed routinely while sampling

Relative density/porosity of granular (sandy) material◊

Relative cohesiveness of clayey formations◊

Ie. Formation compressive strengths◊

Correlated with formation hydrogeologic and engineering characteristics

Attach sampler to the bottom center rod and lower into the hole

◊

Apply a 140lb weight across 30" onto top rod◊

Count blows/foot (300mm) of penetration (N)◊

Remove from hole when full◊

Open, describe and correlate with blow count◊

Record on log◊

Steps:

Split Spoon Sampler□

Pressed into the formation

Sampler with a latching mechanism is placed in the lower auger section using a wireline

Sampler does not rotate with the auger and is pressed into hole as auguring proceeds

Remove with the wireline and replace with another

The sample is relatively undisturbed compared to a split spoon sample

Shelby Tube□

Samplers

Sample collection○

Augers-

Drilling and Wells

Thin wall◊

Not driven◊

The sample is relatively undisturbed compared to a split spoon sample

Means less compaction of the sample◊

Thin walled

High frequency vibrational forces from a hydraulic drill head advance a core bit○

Invented by a Canadian who spent 20 years on it○

Large diameter (up to 8") core samples can be retrieved in unconsolidated formations○

Sonic Drilling-

A 3/4 – 3 ½” sampler is pressed using hydraulic pulldown and percussion @ 50 – 100 feet into the subsurface

○

Can be used in combo with various subsurface sampling and in-situ testing devices○

Direct Push Drilling-

For retrieval of narrow diameter, representative bedrock cores without removal of the drill rod

○

Drilling & coring take place simultaneously allowing you to continue drilling while you sample

○

It is the inner core barrel that accepts the core

Outer barrel and inner core barrel○

PDC core bits are used○

Appendix 3.E on DVD○

Fracture density and rock-mass strength is calculated using the “rock quality designation” equation

○

Sum1 = Sum of length of core segments longer than 4” (10 cm) along the core centerline

□

1Total = Total length of core in inches (cm)□

Where:

More fractured the rock, the lower the RQD value□A higher value means less fracturing

○

Wireline-Core Drilling-

Samples are very valuable○

Sample bags

Identify and document completely and accurately○

Sample Handling Generalities-

Drilling and Wells

Project number□Depth interval□

Sample bags

Project number□Date□Drilling contractor□Drilling method□Drilling rig and driller□Bit specs□Drilling fluid properties□Casing specs□Anything that may affect ROP or sample quality□

Document drilling conditions in the field notebook and litholog

Decant fluid if necessary and mix thoroughly

Do not wash

Dry at low heat in cloth bags

Drilling and Wells

Lowered, pushed, hammered or driven

May be part of the drilling process

May be installed before or after drilling is finished

More than one string can be installed

The process of casing installation varies:○

Casing Installation-

The operation of mixing and placing a grout in a void space○

Grout is fluid mixture of cement or bentonite having a consistency such that it can be forced through a pipe for placement

○

Drilling fluid lost circulation□

Keeping the mine dry◊

Mine shafts

Very common issue in NS◊

Highly turbid water with high coliform count◊

Fractures intersecting with the ground surface

Water intrusion□

Reduce permeability

Inadequate RQDs rock quality designation (rock strength)□Consolidate and strengthen material

Polycyclic aromatic hydrocarbons (from incomplete combustion) & PCBs at the Sydney tar ponds

Solidification & stabilization□

Cutoff walls with a cap□

Isolate contaminants

Grouting may be done for a number of reasons○

Grouting-

Between casing and hole

Between overlapping strings of casing

Filling the annular space outside casing with a slurry of cement or bentonite○

Bentonite (improves hydraulics)

Sand (improves lost circulation)

Plus additives if appropriate□A mixture of Portland cement and water (neat cement)

Cement Slurry○

Puddled clay (viscous mixture, more than drilling fluid, cannot be pumped) hydrated in place to make a typically tight seal

When there is no danger of drying and shrinking and no danger of it being washed away

Bentonite Slurry○

Many defects can be traced to inadequate casing and/or grout

Grout can be used to repair well defects

Grouting is important for the sanitation security of water wells○

Prevents vertical transmission outside the casing□

Protect the water bearing formation and well intake from surface and subsurface sources of contamination

Protect casing from corrosion

Anchors casing (cement not bentonite)

Keeps water from vertically transmitting energy while developing the well□Better well development (cement)

Repair defects

Reasons for grouting well casing○

Well Construction-

Well Completion & Development TechnologyMonday, November 23, 2015 5:40 PM

Drilling and Wells

Repair defects

20' of casing required

Grouting is not

Well construction regulations of the NS environment act□Local standards

Depth to bedrock in bedrock wells

Depth to producing zone in screened wells

Fractures intersecting the ground surface□Faults giving turbid water□Arrangement of formations□Changing water quality with depth□Nearby pollution sources□

That required to seal off problem zones

The length of casing installed and grouted depends on several factors○

Eg. Fractured bedrock with little or no soil cover

Not foolproof ○

Mix of calcium silicates (Ca + Si + O), & calcium aluminate (Ca + Al + O)□Portland cement is a mixture of calcium silicates and calcium aluminates

Limestone provides Ca□Clay provides Al, Si, & O□

Major source of

CaO = quicklime

Heating Limestone @1450C□

Made by heating limestone and clay in a kiln

This dehydrated material is ground and mixed with gypsum

When water is added there is a complex series of hydrolysis reactions and significant evolution of heat

Cement will thereby set (stiffen) in a few hours and continue to harden over the years

□

Ie. There is an increase in compressive strength□

There are different rates of reaction between water and the different compounds present

By coating grains of Ca silicates and Ca aluminates thereby slowing hydrolysis

□Gypsum is added to retard the setting rate

Cement must be kept fluid and of workable consistency while being put into place

□

A compressive strength of ~500 psi after 12-24 hours is desired□

This is important:

Higher T and P speeds the setting rate◊

Temperature/pressure conditions

containing mix water or groundwater◊

◊

Will slow down the curing time because of the forming of gypsum

◊

Chemical environment

Formulated as to:□Difference API classes of cements are made by adjusting the mixture at the factory

1-8% by weight

Takes up any excess water which helps eliminate any shrinkage◊

Reduce water loss and shrinkage

Bentonite□

Siliceous materialDiatomaceous earth□

Cement Additives

Grouting with Cement○

Drilling and Wells

Siliceous material

Lowers density

Helps reduce lost circulation◊

Sand grains help plug off permeability◊

Bridging agent

Sand□

Na & Ca chloride

Speeds the setting rate

Used with high

Accelerators□

High temperature and pressure conditions are managed with this

◊

Gypsum

Slows the setting rate

Retarder□

Downhole physical and chemical conditions

Api class of cement and on-site additives needed□

Calculate, tables, caliper log data

Hole washouts◊

Lost circulation◊

Use a safety factor of ~25%

Amount of cement□

Want an annular space of 2-4"◊

Hole diameter will have to be 4-8" greater than the casing OD◊

Can dictate the size of the annular space needed and hence hole size, drilling method, and casing installation method

Make sure equipment is onsite

Cement mixing and placement method□

Dictate rig specifications–

Heavy/thick walled casing

Long lengths of casing needs high collapse strength◊

Collapse strength of the casing

Casing specifications□

Planning stage

5.2 U.S. gallons (19.6L)/94lbs (sack of cement)□This will completely hydrolyze the cement and result in a slurry density of 15.6 ppg ('neat' cement)

□

Higher water contents result in shrinkage□

Proportioning the cement

Has to be thoroughly mixed and free of lumps and rocks□Grout machines combine mixing and pumping □Portable cement mixers, cement trucks, shovel/tank are also options□

Mixing the cement

Imperative: one step operation□

Use of casing centralizers are a must

Center casing□

Turbulent flow: removes water, drilling fluid, cavings

Laminar flow: will not clean the annular space sufficiently

Introduce from the bottom up under turbulent flow with a positive displacement pump

□

Backfill open hole with mortar sand

Use an external packer with float shoe

Cement baskets

With open hole/screen below casing□

Placement

Divided into:○

Cementing Operations-

Drilling and Wells

Cement baskets

External Packer with float shoe□

Drill to depth

Install drillable (cement) plug at bottom of casing

Anchor with drilling fluid or water□Lower casing with centralizers into hole

Install grout (tremie) pipe in annular space

Cement is pumped down the tremie pipe until cement appears at the surface

□

As the cement rises, so will the pressure on the pump□Pump pressure = hydrostatic pressure of the end of the tremie pipe + friction losses inside the pipe + annulus

□

May have to raise the tremie pipe as cement rises in the annulus□

Avoids gaps or voids in the annular space

Always keep the tremie pipe submerged in the cement□

When the plug of cement is being drilled out, if bentonite is used the calcium in the cement will cause it to flocculate the drilling fluid

□

Tremie Pipe is about 1-2" in diameter

Tremie Pipe outside casing method ○

Slurry placement methods-

Drilling and Wells

calcium in the cement will cause it to flocculate the drilling fluid

Cement appears at surface □There is none left to pump□

Pump cement until:

A 'top' job may be necessary

Wait for cement to set up and drill out cement at shoe

For greater depth and volume to be pumped

A drillable plug with a check valve

Install float shoe at the bottom of casing string□

Anchor casing by periodic filling of casing with water or drilling fluid

Suspend casing with casing slips

Install grout (drill) pipe and attach to float shoe

Mix and pump required volume of cement using a grout machine

Water in the drill pipe; inside the pipe to displace required amount of cement

◊

Displace cement with water

Cement appears at the surface◊

Pump strokes indicate displacement water is at the shoe◊

Get to casing shoe and then stop or to the surface

Do not over displace◊

May need 'top' job using the tremie pipe outside casing method◊

Pump until:

Detach grout pipe and reverse circulate out excess cement inside grout pipe

Wait for cement to set up and drill out

Lower casing with centralizers into hole□

Steps:

Tremie Pipe inside casing method○

Drilling and Wells

For greater depth and volume pumped

The first plug separates the cement slurry from the drilling fluid□The second separates the slurry from the displacement water□Plugs are stored in a casing head at the surface□

Lower casing into hole and suspend with casing slips

Circulate to clean annulus

Insert first plug

Pump required volume of cement

Insert second plug

Do not over displace◊

Displace with water to bottom of casing

Apply back pressure on pump

Perform 'top' job if necessary

Wait on cement and drill out

Steps:□

Two rubber plugs are used inside the casing

Casing Method○

Common Cementing Failures-

Drilling and Wells

Not enough retarder □Cement freezes up before you get it into place

Premature setting○

Not enough accelerator (Ca)

Partial Setting○

Insufficient grout length○

Gaps in cement○

Excess non-reacted water

Shrinkage○

Collapse strength has to be able to withstand pressures

Casing collapse○

Common Cementing Failures-

If water table is low: fill casing□

Water will U tube into the casing if there is a leak

If water table is high: empty casing□

Monitor water well level change inside casing

Pressurize inside casing @ 7-10 psi□Should hold for one hour□

Pressure test

Check for gaps by measuring interval transit time□Also called a cement bond log□

Acoustic log

As cement cures it releases heat□Temperature survey

Use respectable FOB/RPM and monitor ROP□Test by drilling

Methods○

Testing Cement Grout-

Substantial expansion makes for a nice tight seal□Effective

Don’t have to worry about it freezing up before it is in place□Easy to use

Bentonite is widely used for grouting water and monitoring wells○

Hydrates and expands in place□Shallow wells only□

Pour dry bentonite into annulus and tamp into place with a pole/rod

Preferred□Mix with water and pump into place using the tremie pipe outside casing method

Placement Methods○

Installation of Bentonite Grout-

It will stick and bridge off above required depth if dry material is poured in place

The high proportion of bentonite to water results in a very high viscosity water

□It may become unpumpable with tremie pipe method

It hydrates quickly○

Use bentonite in granular, pellet or chip form

Cool bentonite on dry ice

Use bentonite with a 'gel cap' coating

Add liquid polymer to the mix water at a ratio of 1:420 by volume

Hydration and expansion is completed in place□All methods slow the rate of hydration

Solutions○

Bentonite can be gently mixed and pumped in batches to minimize viscosity□Not restricted to a one step operation□

Mixing

Mixing and proportioning bentonite grout○

Proportioning

Inherent problem using bentonite-

Drilling and Wells

Less than 1.5 ppg = excessive shrinkage□

1.5 ppg bentonite (pounds of bentonite per US gallon of water) is needed to prevent shrinkage

Results in excessive viscosity for pumping @ 1.5 ppg (1.5ppg x 42 gal/bbl = 63 pounds/barrel)

□Problem

Add liquid polymer at 1:420 by volume with water□Solution

Proportioning○

6-8x expansion (or more)□Makes tight seal

Not restricted to one step operation□Easy to use

Don't have to wait 12-24 hours (500psi)□Sets quickly

Less expensive than cement

Important with plastic casing□Exerts a lower hydrostatic pressure @ 9.2 ppg

Important with plastic casing□No heat of hydration

Advantages of bentonite grout○

Use cement□Can dry and shrink above the water table

Does not anchor casing

Clays will aggregate & flocculate◊

Hard water or mix water that is hard, will maximize the expansion

Hard water, organic acids□Subject to contamination

Can wash away

Especially metals analysis□Can put a finer sand on top of the gravel pack in order to prevent ground from getting into the well

□

Can alter chemistry of monitoring well samples

Limitation○

Drilling and Wells

Casing○

Screened

Open hole

Intake○

Two basic elements to consider in well design-

Lower turbidity

Lower pump damage

To provide filtration of sediments

To provide formation support

Intakes in unconsolidated and semi-consolidated formations are screened○

When dealing with friable or weakly cemented sandstone formations

Causes silica & calcite cements to dissolveo

Dramatically speeding up groundwater flow, short circuiting the hydrologic cycle which makes water becomes under saturated with respect to surrounding geologic material

Changing groundwater chemistry in response to pumping the aquifer

The Wolfville & carboniferous Pictou formations are commonly screened

Bedrock wells are usually unscreened○

Minimize drawdown for a given well yield

Well hydraulic efficiency

Electrical costs will increase

Reducing operational and maintenance cost

Screen design can influence maintenance costso

Corrosion

Incrustation of the well

Long well life

Well screen design is vital regarding:○

At least 20% open areao

To at least match formation % porosity

Less head loss/friction loss/drawdown at well intake

Provide large % open area

Attributed of good well screen design:○

Screens-

Water Well DesignSunday, November 29, 2015 5:47 PM

Drilling and Wells

o

Maximize hydraulic efficiency and well specific capacity

During well development and subsequent production

Prevention of sediments plugging off screen openness

Non-clogging

Tremendous surge pressure makes it easy to collapse the well screen

Surge block developmento

To withstand earth pressures and well development pressures

Strong

Provides both good filtration & good hydraulic efficiencyo

Slot size conducive to grain size distribution

Prevent sand pumping

Facilitate transfer of hydraulic energy to the formation

Around the entire circumference of well screen

Permit good well development

Relates to hydraulic efficiency and reducing the drawdown/ pressure drop on the water at the well intake

Pressure on the water is being decreased causing the degassing of

The pressure is lowered causing a degassing of

On a confined aquifer

Minimize incrustation

Drilling and Wells

The pressure is lowered causing a degassing of o

Causing scaling on the well intake

Screen material has to be consistent with the chemical environmento

Lithotrophic bacteria o

Natural carbonic and mineral acids

HClo

o

o

- Granular acid (sulfamic) o

Strong acids introduced to remove scale

Acids

O2 rusting

Oxidation

Hydrolysiso

+ = scale forming

= Corrosive water, susceptible to oxidation & hydrolysis-

pH, calcium hardness, TDS, alkalinity are all factors of the langlier index

-

Chemical corrosion tendencies can be measured using the Langelier Index

o

Chemical corrosion

Screen material has to be consistent with the Galvanic serieso

Provide different capacities to conduct an electrical current and therefore a voltage potential

Dissimilar metals in contact with one another according to the Galvanic series

An electrolyte solution to conduct an electrical current from the anode to the cathode which has the higher electrical conductivity

Electrons, along with H+ and other cations (Fe+++) leave the anode maintaining electrical neutrality and causing pitting

Metal is removed from the anode

H2 film

Fe(OH)3, Fe2O3 o

Rust tubercles

Material is deposited at the cathode

Requirementso

With this, the greater the rate of corrosion

Metal is removed on the anode side

On the cathode side, a metal film builds

Causes pitting on metal surfaces when metals are corroded or through electrochemical means

Wider the separation of metals the larger the voltage potentialo

Provide zinc or magnesium anode which makes iron the cathode, thereby limiting corrosion

o

Example, Hot water Tank

Make the metal you want to protect the cathode by providing a sacrificial anode

Cathodic Protectiono

Electrochemical corrosion

Minimize corrosion

Drilling and Wells

the cathode, thereby limiting corrosion

Most widely used

Made by winding “v” – shaped wire around a circular arrangement of longitudinal rods

The wire, with the wide side to the outside, is welded to the rods to make a strong, light-weight non-clogging structure

Important for good sand control

The slots are made by spacing the wire to close tolerances on successive turns

Slot size can be adjusted accurately according to the grain size distribution of the formation material

No. 20 slot screen = openings are 20 thousandths of an inch (0.020 inch) wide

Slot sizes are designated by numbers corresponding to opening width in thousandths of an inch

This corresponds to the number of openings per linear inch

Compare with the “mesh” number or “gauze” number or “sieve” number for wire mesh screens

Continuous slot well screens provide a large % open area around the entire screen

Continuous Slot Well Screenso

Types of Well Screens-

Drilling and Wells

Easy to exceed formation porosity

Continuous slot well screens provide a large % open area around the entire screen circumference

Large open area = lower entrance velocity of water through the screen resulting in less friction loss and drawdown

o

Result: higher well specific capacity and lower operational costso

Hydraulic efficiency

Large open area around the entire screen circumference for transmission of hydraulic energy

o

Good well development

The large open area and low entrance velocities result in less drawdown around the well and hence less of a pressure drop on the water for degassing of CO2

o

Incrustation is minimized

The large open area and low entrance velocities result in less water (and hence H+ and O2 ) coming into contact with slot metal surfaces over time lessening corrosion rates

o

(Chemical) Corrosion is minimized

The large % open area of continuous slot well screens has many benefits:

For a given design pumping rate, screen slot size and screen diameter determine the screen length that will provide the total open area for an entrance velocity of 0. 1 ft./ sec

Continuous slot screened intakes are designed for a maximum entrance velocity of 0.1 ft/ sec

Optimizes for hydraulic efficiency and well development while minimizing corrosion and incrustation

For screens that are to be telescoped through casing

The size designation corresponds to the nominal casing inside diameter through which it is to be placed

eg.: a 4” telescope size screen actually has an OD 3 ¾”

Telescope size serieso

For screens that are to be run along with the casing in one operation

Have the same nominal ID as the corresponding nominal ID of the casing

A 4” pipe size well screen has a nominal ID of 4”

Pipe size screen serieso

Two series:

Continuous Slot Screen Diameter

Stainless steel, low carbon steel, PVC

Continuous Slot Screen Material

One screen telescoped inside another with the annulus filled with well rounded pack material

Strong, hydraulically efficient, convenient

Pre-pack Screenso

Slots are made with a power punch

Less control over slot sizes

Prone to clogging

Low percent open area

Low strength

Poor well development

Limitations:

Best in gravel packed wells

Louvered and Bridge Slot Screenso

Vertical slots made with a cutting torch

Limitations as per louvered and bridge slot screens

Slotted Steel Pipeo

Drilling and Wells

Limitations as per louvered and bridge slot screens

Inner perforated pipe

Outer continuous slot screen

Two parts:

Strong, good sand control

Poor hydraulic efficiency

Pipe-Base Screenso

Commonly used in monitoring wells installed in clay-rich surficial deposits

Low open area

Slots are not continuous

Filter packed with silica sand

Slotted PVC Plastic Pipeo

Continuous Slot Wire–Wrapped PVC Screeno

Continuous slot

Wire mesh

Well Pointso

Placement in the aquifer

Slot size

Length

Material

An efficient, long lasting, ~maintenance free, screened well requires optimum screen: o

The screen should be placed in lower zones having the highest K

Unconfined Aquifers

Place screens in zones of highest K below the top of the aquifer

Confined Aquifers

Screen Placemento

Natural development

Filter packing

Slot selection is a function of the method of well completion

Well Screen Slot Selectiono

The formation is coarse grained and non-homogeneous having a wide size distribution

Typically: choose a slot size corresponding to the 40% retained size of the sieve analysis

Natural development

The completion method depends on the nature of the aquifer material and the grain size distribution

o

Slot size can be varied along the length of screen according to changing formation grain size distribution

Adjust the slot size so as to be conservative to reduce development time and chance of sand pumping

Larger slot sizes require a longer development time

Sample reliability

Extend about 3 feet of the screen designed for the finer material into the coarse material

Accommodates for slumping during development

If a fine layer overlies a coarse layer

Fine, low K zones can be blanked off

Other considerationso

Continuous Slot Screened Well Intake Design-

The formation is fine grained (40% retained size <0.01”) and homogeneous (uniformity coefficient less than 2.5) or if the formation is highly laminated

o

Filter Packed-

Drilling and Wells

Favours filter pack

Very fine with a high uniformity (low uniformity coefficient)

A ~uniform, clean, rounded quartz sand is placed outside the screeno

Less restrictive to flow

Much larger screen slot sizes can be used

Creates a high K sheath of porous and permeable material around the well screen

Increases well specific capacityo

Filter pack acts as a filter

Lessens potential for sand pumpingo

Without filter pack, some wells would take days to develop

Decreases development timeo

Lessens slumping

Filter packing prevents/lessens this occurrence

Plugs off permeability when the fine formation slumps into the well

Stabilizes the formationo

Advantages to Filter Packing-

Choose intervalo

Use blanks in unproductive zones

Focus on finest material in that intervalo

4 – 6 if the 40% retained size is 0.01” or less and the uniformity coefficient is 2.5 or less

6 – 10 as samples become increasingly non-uniform

Multiply the 70% retained size by a factor between 4 -10o

Place the result from above as the 70% retained size of the filter pack materialo

Through this point draw a line representing a uniformity coefficient of ~ 2.5 o

Select a screen slot size that retains 90% of the filter packo

Size of the annular space outside of the well screen

Determine pack volume requiredo

Some slumping will occur because 10% of the filter pack will enter the well during the developing process (90% retained)

Extend pack above the screen to compensate for settling o

Develop wello

Steps in Filter Pack Design-

The pack is designed to retain formation particlesFilter Pack Thickness-

Drilling and Wells

Requires a thickness of only ~1/2 inch

The pack is designed to retain formation particleso

Hydraulic energy will not be able to restore the well back to efficient levels (pre-drilling state)

Too thick a pack = harder to remove formation drilling damage when developing the well

Best to use at least 3 inches to ensure complete envelopmento

Use centralizerso

Placed around screens that are to be developed naturally if the hole is more than ~2 inches larger than the screen

o

Functions to lessen slumping of the formation around the screen during development to maintain natural stratification and K

o

Use rounded quartz sand that has an overall size somewhat larger than the formationo

Formation Stabilizer-

Type of aquifer

Unconfined

Confined

Optimum screen length is based on:o

Thickness of the aquifer or water bearing zone within the aquifero

Required well yieldo

Place screens in lower zones having highest K

Greater total screen open areao

Less flow convergence toward the well intakeo

Less frictional resistance to flow

Less drawdown

Shorter flow path lengtho

Increase well specific capacity by reducing drawdown for a given well yield

Total available drawdown = distance of SWL to the top of the pump (best inside casing above the screen)

By reducing the total available drawdowno

But: longer screens also reduce the maximum well yield possible

Longer screens:

Unconfined Aquiferso

Higher open area

Less flow convergence

Shorter flow path length

~ the entire interval can be screened to maximize well specific capacity

Confined Aquiferso

Screen Length-

Drilling and Wells

Use blanks in unproductive intervals

Focus on high K zones

Wells are designed for the pump to be set above the screen inside the casingo

Flow path is lengthened

Only partially screening results in too much frictional resistance to flowo

Pump intakes need room; much of the water comes from within the well (when the pump is turned on)

Nominal minimum of 2" larger than the nominal diameter of the borehole

Increasing screen diameter has little effect on increasing screen open area and well specific capacity relative to the increased cost of drilling and constructing a larger diameter well

o

A = 2πrh

Surface area of a screen (cylinder):o

More cost effective to increase the screen length as opposed to well radius to increase open area

o

Screen diameter is dictated by casing diameter which, in turn, is dictated by the size of the pump needed for the anticipated well yield

o

Screen Diameter-

The screen should be designed for an entrance velocity less than 0.1 ft/ sec (3 cm/ sec)o

This ensures laminar flow at the well intake and optimizes for well hydraulic efficiency while lessening

o

Greater hydraulic efficiency

maintenance and operational costs

Screen Entrance Velocity-

Drilling and Wells

Greater hydraulic efficiency

Lowers incrustation & corrosion

Pumping rate

Slot size

Screen diameter

Slot size & screen diameter are two variables that cannot be changed after drilling the well

o

Screen length

Total screen open area:

Entrance velocity is a function of:o

V = Entrance velocity (ft/ sec)o

Q = Pump rate (ft3/ sec)o

A = Total screen open area (ft2)o

Where:

V = Q/ A

Average entrance velocity is determined by dividing the anticipated well yield by the total screen open area

o

1 US gal = 0.883 ipgmo

STC = U. S. gpm/ ft. of screen length at an entrance velocity of 0.1 ft./ sec o

Determined by multiplying the in.2 /ft. of screen open area by 0.31o

CD Appendix 9.K “Screen Brochure”

Screen manufacturers provide data on screen open area in terms of sq. in. per foot of screen length

o

Screen transmitting capacity can be used to determine the length of screen necessary for an entrance velocity of 0.1 ft./ sec to accommodate a required well yield

o

* 100%

Screen open area (sq. in. per foot, cm2/ m) can also be calculated when the slot size and wire face width are known

o

=

Necessary adjustments to screen length to provide the required open area for the recommended entrance velocity can be found from:

o

Anticipated well yield should equal 0.1 US GPM

Determining feet of screen required:o

Screen Transmitting Capacity (STC)-

Diameter

Depth

Material

Three major considerations:o

Casing Design-

Has to be large enough to accommodate the size of the pump required for the anticipated well yield

Main criteriono

Optimum is 4" larger than the inside casing diameter, allowing for 2" on either side of the pump

Casing diameter should be at least 2 nominal sizes larger (in inches) than the nominal diameter of the pump required

Rule of thumb:o

Especially if the well is out of alignment

Ease of pump installation

This permits:o

Casing Diameter-

Drilling and Wells

Especially if the well is out of alignment

Less frictional resistance to flowo

Reduced pressure losses as water passes downward past the pump bowls when the pump is first turned on

The upward velocity from the well intake to the pump intake once the pumping water level stabilizes should be no more than 5 ft/ sec to limit friction losses

eg.: running linerso

Greater well diameter allows for more room to manoeuvre for well rehabilitation purposes

Hydraulic efficiency

Well planning is needed regarding casing diameter, hence well diameter

Telescoped screens

Casing ID is often larger than that of the screen

Less potential damage to the well screen during pump installation and removal

Less turbulence at the well intake

There is no sense in having the pump set in the screen section in a properly designed well

The pump is usually set in the casing section in screened wells:o

Increases the total available drawdown and hence the maximum well yield possible

Usually set 5ft from the bottom of the well to avoid pumping sediment

Makes use of well storage in low yield bedrock wells

In unscreened bedrock wells the pump can be set near the bottom of the well in the open hole below casing

o

Depth to producing zone in screened wells

Depth to the bedrock in bedrock wells

That required to seal off problem zones

Regulations

Dictated by:o

More than one casing string may be installed o

Casing Depth-

Strength requirements

Collapse

Pulling strength; long strings of casing can cause the casing to snap off

Tensile

Bending strength; used in deviated boreholes

Yield

Chemical

Plastic casing or steel casing with grout help with both of these corrosion issues

o

Electrochemical

Corrosion control

Cable tool drilling method requires thicker casing

Drilling procedure

NS Well Requirements of the Environment Act

Regulations

Dictated by:o

Steel

Low carbon

Stainless

PVC, ABS, SR

Plastic

Casing material optionso

Casing Materials-

Casing Size DesignationSteel Pipe Specifications-

Drilling and Wells

For pipe sizes up to and including 12 inches nominal ID, pipe is designated according to its nominal ID

Wall thickness

Weight

Collapse strength

The actual ID varies as to

Casing Size Designationo

A somewhat arbitrary designation having to do with wall thickness for a given pipe size

For a given pipe size higher schedule numbers correspond to increasing wall thickness, weight and collapse strength

Schedule numberso

Increasing pipe diameter results in decreased collapse strength for a given wall thickness

Wall thickness has to increase with diameter in order to maintain collapse strength

Note:o

Wall thickness

Weight

Collapse strength

ID is variable as to

Called large diameter pipe

For pipe sizes larger than nominal 12 inches ID pipe is designated by its actual ODo

Standard (STD)

Extra heavy (XS)

Double extra heavy (XXS)

For both large and small diameter pipe there are other weight classes in addition to schedule numbers

o

American Society for Testing and Materials (ASTM) and the American Petroleum Institute (API) fall under this umbrella

ASTM criteria usually followed

Casing and pipe specifications are set by the American National Standards Institute (ANSI)

o

Determines the type of steel or alloyo

Grade A vs. Grade B steel reflects variations in C, Mn, P and S contento

Collapse, tensile, yield

Grade B is stronger

Affects strengthso

An alloy of chromium (usually) with other metals and steel for corrosion resistance

Very high cost

Stainless steel:o

6 inch nominal diameter

Minimum length: 20 feet

ASTM Grade B steel

Standard weight and wall thickness (minimum 0.185 inch)

Minimum 6 inches AGL

Plain end pipe normally

Steel casing specifications for domestic water wells according to the Well Construction Regulations of the Nova Scotia Environment Act

o

PVC (polyvinyl chloride) (commonly)

ABS (black pipe)

SR (styrene rubber)

Choices include:

Corrosion resistant

Major advantages:

Thermoplastic Casingo

Chemical Composition of Steel Pipe-

Drilling and Wells

Corrosion resistant

Light weight

Easy to install

Resistant to acid treatment

Lower strength

Major drawback:

Specifications are laid out by the ASTM

Commonly used plastic pipe specification

Ratio of pipe OD/ wall thickness

eg.: SDR21

Standard dimension ratio:

Higher SDR = lower collapse strength

Lower SDR = higher collapse strength

For the same wall thickness, the SDR will increase as casing diameter increases corresponding to a decrease in collapse strength

Grouting concernso

Lower collapse, compressive and tensile strength

Use centralizerso

Very flexible

Aggravated by cold and UV lighto

Low impact resistance

Low heat resistance

Precautions re use of plastic casing

Threaded and coupled

Locking devices

Mechanical

Solvent cement

Joining Plastic Casingo

Drilling and Wells

"Many special additives, such as flocculants, thinning agents (dispersants), weighting materials, filtrate reducers, lubricants, and lost-circulation materials, are used to further adjust the properties of drilling fluids." (288-289)

a.

"A freshwater-based drilling fluid is a mixture of a freshwater continuous phase with clays, polymers, surfactants, and other conditioning additives combined (as necessary) to impart the desired properties to the drilling fluid." (289)

b.

What is the general function of drilling fluid additives?1.

Equipment availablea.Remoteness of the drilling siteb.Water suppliesc.Environmental regulationsd.Experience of the drilling crewe.

List 5 factors that influence the selection of drilling fluid systems.2.

"Regardless of which drilling-fluid system is used, its effectiveness depends upon the drilling professional's ability to anticipate the chemical and physical changes taking place during drilling and to make system modifications as required." (295)

a.What general aspects determine the success or failure of a drilling fluid system?3.

Clean the bit and the borehole bottoma.Stabilize the boreholeb.Cool and lubricate the drill bitc.Control fluid lossd.Drop cuttings into the settling pite.Provide information about the wellboref.Suspend cuttings in the boreholeg.Control the formationh.Maximize productivityi.

List the main functions of water based drilling fluids?4.

Densitya.Viscosityb.Yield Pointc.Gel strengthd.Filter cake and fluid losse.pHf.Calcium contentg.Sand contenth.

What are the important physical properties of water based drilling fluids?5.

a.

The water table is at a depth of 10 feet in an unconfined aquifer. What is the formation pressure (in psi and kPa) at a depth of 150 feet?

6.

Under-compacted - Results in pore fluids taking a portion of the overlying weight of overburden.

i.

Confined - Characterized by an overlying hydraulic barrier. This prevents formation pore fluids from being squeezed out with an overlying weight.

a.

Unconfined - Supported completely by grain to grain contact.b.

Why are formation pressures in confined aquifers greater than those in unconfined aquifers for a given depth?

7.

10.5-11 ppg maximum - anything above this you will need barite.i.Maximum practical densitya.

What is the problem if a higher density is attempted using bentonite and drilled solids b.

What is the maximum practical density that can be used with a low density solids (bentonite and/or drilled solids only) drilling mud? What is the problem if a higher density is attempted using bentonite and drilled solids only?

8.

Assignment: Water Based Drilling FluidsSunday, November 29, 2015 2:31 PM

Drilling and Wells

"To increase density any further but maintain a proper solids-fluid ratio, higher-density material must be introduced so that a lesser quantity of solids (by volume) is needed to achieve a specific density." (298-299)

i.

What is the problem if a higher density is attempted using bentonite and drilled solids only?

b.

"Soluble salts such as sodium chloride (NaCl) and calcium chloride ( ) are useful for weighting some drilling fluids that are made with polymeric additives."

a.How can the density of polymer drilling fluids be increased?9.

i.

ii.

You are about to penetrate a confined aquifer at a depth of 75 meters. The potentiometric surface at the site is known to be 6.0 meters above ground surface. What is the formation pressure (psi & kPa) at the top of aquifer?

a.

i.

ii.

What is the formation pressure 5 meters below the top of the aquifer?b.

Question10.

Removal of the drilling fluid and cuttings during development can be extremely difficult, especially if clay is present.

i.Large volumes of drilling fluid and cuttings can be forced into the aquifer during drilling. a.

Material costs increase because of high fluid losses, particularly in areas where mix water is expensive or must be transported great distances.

b.

Rate of penetration is reduced. As cuttings are created by the bit, the hydrostatic pressure on the bottom of the borehole pushes down on them and impedes their removal from the borehole.

c.

Sample collection is more difficult and less reliable, because cuttings do not drop out of the drilling fluid at the surface and instead intermingle with the samples collected.

d.

Mud pump wear is increased because the pump must keep recirculating a high volume of unnecessary solids.

e.

Pumping costs increase because solids are continually recirculated and circulation of heavier fluids requires more energy.

f.

List 6 adverse factors relating to poor drilling fluid solids control.11.

"The viscosity of a drilling fluid with clay additives also is a function of the rate at which the fluid is pumped. At lower velocities the viscosity is higher because it is governed by the charges of the plates; at higher velocities the charges of the plates have less effect." (302)

a.What is the relationship between viscosity and shear rate for shear thinning drilling fluids?12.

55-65 secondsa.What marsh funnel viscosity is generally required to drill coarse sands?13.

Viscous nature of clay additive drilling fluidsa.Positively charged edges and negatively charged surfaces causing the particles to be "strongly attracted to-or repulsed by-each other and various other substances." (302)

b.

What features of sodium montmorillonite enhance its use as a drilling fluid additive?14.

Does not need to be completed.i.Describe the nature of Revert as a drilling fluid additive.a.

Reverti.Sodium polyacrylates (SPA)ii.Polyanionic cellulose (PAC)iii.Partially hydrolyzed polyacrylamides (PHPA)iv.

Name four commonly used drilling fluid polymers.b.

Question15.

"They can provide viscosity modification (thickening or thinning it), shale encapsulation, filtration control, friction reduction, and improvement of foam qualities." (306)

a.What are advantages to use of low solids/gel strength drilling fluids such as revert?16.

What are the features of a good filter cake?17.

Drilling and Wells

"Each of the insol particles is covered with a relatively thick, viscous film of fluid produced by the dissolved sol particles-and, as insols build up on a borehole fluid is prevented from leaving the borehole. Thus, fluid loss can be controlled with a relatively thin coating on the wall of the borehole. A thicker layer of clay particles might be required to achieve the same fluid-loss properties. In general, polymeric films are much thinner than the filter cakes created by clay particles, even though the water-loss characteristics are the same." (312)

a.What are the features of a good filter cake?17.

pH - "Most drilling fluid additives perform best in water having a pH range of 8.5-9. In general, the lower the pH, the more likely it is that the water has high concentrations of ions such as calcium and magnesium in solution (hard water)."

a.

Hardness - "Clay yields can be increased and water losses decreased if hard water is softened before it is used for mixing the drilling fluid."

b.

"Polyvalent metallic ions can be removed from water by chlorination at a 50ppm concentration." (317)

i.

Metallic ion concentrations - "The hydration potentials of colloidal additives are significantly reduced if metallic ions occur at high concentrations. If iron concentrations are 3ppm or greater, for example, then the viscosity buildup in a natural organic system could be retarded."

c.

What 3 aspects of drilling fluid mix water quality are particularly important and why?18.

"The principal objectives for the pit are storage of an adequate volume of drilling fluid and to act as an effective settling basin for suspended cuttings." (318)

i.What is the function of mud pits?a.

"The size of the mud pit is dictated by the volume of drilling fluid contained in the finished borehole and the need for a reserve volume, which varies according to the particular rotary system used. Usually the volume of the pit is 1.5 to 3 times the volume of the finished hole." (318)

i.What determines the size of the mud pit required?b.

What is the function of mud pits? What determines the size of the mud pit required?19.

Aggregated-flocculateda.Aggregated-deflocculatedb.

Greatest gel strength occurs when the drilling fluid is in the dispersed-flocculated state.

i.Dispersed-flocculatedc.

Dispersed-deflocculatedd.

With regards to the arrangement of clay particles, what possible physical conditions can be exhibited by a bentonite drilling fluid?

20.

Drilling and Wells

Fast rates of penetration in consolidated rocka.Simpleb.

What are two general advantages to use of air drilling systems?1.

Volumea.Pressureb.

What two components of air supply must compressors provide for effective air drilling?2.

The compressor can take 1100 cfm, under atmospheric conditions, and compress it to 150psi and deliver it every minute

a.

A certain compressor has a capacity rating of 1100 CFM and 150psi. What does this mean the compressor is capable of doing? (328)

3.

Higher pressure = less volume outputi.Rise in elevation = less volume outputii.

How does air temperature and elevation affect compressor output?a.

0.89i.

The elevation above sea level is 600 meters and the air temperature is 27C. What is the correction factor for compressor output? (Table 329)

b.

Question4.

Increases pressure outputi.In seriesa.

Increases volume outputi.In parallelb.

What is the effect of connecting compressors5.

Stop drilling and run the compressor, the hole should clean up in 7 seconds per 100 feeta.

What simple method can be applied at the well site to determine if enough air is being supplied for cuttings removal?

6.

More air is needed as boreholes deepena.30-40% more air is required when drilling with air-mist systemsb.Can be used to overcome static heads following a temporary cessation of drillingc.For down-hole hammers, higher pressure translates into higher rates of penetration rates when drilling with dry air because the hammer action is faster

d.

List four conditions that may lead to increased compressor pressure requirements? (330)7.

Air only (dry air)a.Air-mistb.Air and small volume of waterc.Air, a small volume of water, and a small amount of surfactantd.Air-foame.Stable foam-air and surfactantf.Stiff foam - air, surfactant, and high molecular-weight polymer or bentoniteg.Aerated drilling fluid - water based drilling fluid and airh.

There are several possible methods available when air is used as the base drilling fluid. What are they? (330)

8.

The column of air puts minimum pressure on the bottom of the borehole. As removal of the rock overburden proceeds, the cutting become progressively easier to chip off because the overlying weight of the rock is reduced (less chip hold down).

a.Give two reasons why air based drilling fluids result in a faster ROP. (330)9.

Hole size = 8.5"a.Casing ID = 9.625"b.DC OD = 6.0"c.DP OD = 4.5"d.Compressor output = 34 m3/mine.

Given10.

Assignment: Air Based Drilling FluidsDecember 7, 2015 12:48 AM

Drilling and Wells

Compressor output = 34 m3/mine.

DC/OH - 6073fti.DP/OH - 4225ftii. iii.

What is the annular velocity in each hole section?f.

Air - water based fluids would result in too much lost circulationi.What is the preferred drilling fluid when drilling highly fractured crystalline rocks?a.

"To overcome this problem polymers and water sometimes are added to the air. The thin polymeric film seals the formation pores and minimizes air loss.

i.

What options are available when drilling highly permeable sandstones and dry, permeable overburden? (332)

b.

Question11.

Hole size = 6.75"a.Drill pipe OD = 3.5"b.Depth = 500'c.

568(Standard cubic feet per meter)i.What is the minimum air volume requirement for dry air drilling? (table 333)d.

Given:12.

Adding small amounts of water to air creates an air-mist system, which helps control dust and to break down any mud collars forming on the drill rods.

a.What is air-mist drilling? What is the purpose for using an air-mist system? (335)13.

Water + Surfactant added to the air systemi.What is an air-foam drilling system? (334)a.

Higher solids-carrying capacityi.Ability to lift large volumes of waterii.Reduced air-volume requirementsiii.Reduced erosion of poorly consolidated formationsiv.Effective dust suppression v.Increased borehole stabilityvi.

What are advantages to using air-foam drilling systems? (335)b.

Question 14.

"The addition of high-molecular weight polymers or bentonite increases the viscous qualities of foam, reduces uphole velocity requirements for effective penetration and adequate cleaning, helps stabilize the borehole walls, and can reduce friction in the borehole.

i.

What is the purpose of adding bentonite and/or polymer to air-foam drilling systems? (338)

a.

"Bentonite cannot be added to an air-foam system if a downhole air hammer is being used, however, because the clay particles rapidly can cause the hammer to malfunction.

i.

What is the problem regarding use of clay additives when drilling with a down-hole hammer? (337)

b.

Question15.

Use a sketch to describe relative temperature, pressure and volume changes that take place with air based drilling fluids along their flow path. (350)

16.

Drilling and Wells

a.

i.

b.

Assuming idea gas conditions, what approximate expansion is associated with air-based drilling fluids between the bit and surface if air is delivered to the bit at an absolute pressure of 125 psi?

17.

What is the recommended up hole velocity when using the following drilling fluids? How much of the appropriate additives are needed to produce a viscosity of 35-55 seconds/quart?

18.

a.

The static water level in the borehole is 55.0 meters from the bottom of the hole. What is the minimum air pressure that must be delivered to the bit to overcome the static load so that drilling can resume?

19.

Drilling and Wells

Rotative - The bit rotates on the bottom of the hole.a.Percussive - The bit has a primarily reciprocal up and down motion.b.

What are the two broad categories of drilling methods? Describe each in general terms.1.

Rotation functions to keep straighter holes & expose new material to the bit.i.What is the function of rotation in percussive drilling methods?a.

Contributes to fragment production in low compressive i.plastic material.ii.

What is the function of rotation in rotative drilling methods?b.

Question 22.

The bit has a primarily reciprocal up and down motion1)High FOB and low RPMi.

What causes penetration in percussive drilling methods?a.

The bit rotates on the bottom of the hole1)Low FOB and High RPMi.

What causes penetration in rotative drilling methods?b.

Question 33.

Dependent on compressor or pumps outputa.

Cross sectional area of the annulus i.Dependent on the size of the boreholeb.

What two factors control flushing fluid annular velocity?4.

Viscosity/Densitya.Annular Velocityb.

What two factors control flushing fluid carrying capacity?5.

Four inch holes to ~175 feet.a.

Hole Depth: A reduced ROP with depth which becomes uneconomicali.Hole Diameter: Limited by annular cleaning capabilityii.

Limitations: b.

What is the limitation to hole diameter when using the hydraulic drilling method? What limits the hole depth attainable?

6.

The cuttings will not be forced out of the borehole and will impede further penetrationa."Obstacles encountered when using air drilling (especially dry-air drilling) usually involve an insufficient air supply that results in an annular velocity that is inadequate for carrying the cutting to the surface. For a given borehole diameter, hole depth is a primary factor affecting cuttings removal because it directly relates to air-volume requirements." (Page 333)

b.

What is a possible consequence of maintaining an annular velocity below optimum?7.

Maintain hole integrityi.Prevents lost circulationii.

Prevents highly turbid water from forming in the well due to surface water contamination1)Minimum 20' in Well Construction Regulations of the NS Environment Act2)

Protect the water supplyiii.

Well screen is tied or screwed into the bottom of the well casing and lowered into the borehole1)Used in combination with well screens in unconsolidated formationsiv.

List reasons for installing casing when drilling water wells with the hydraulic rotary method?a.

Maintain hole integrity - In unconsolidated formations casing is driven as drilling proceeds to keep the hole open.

i.

Prevents lost circulationii.

Prevents highly turbid water from forming in the well due to surface water contamination1)Minimum 20' in Well Construction Regulations of the NS Environment Act2)

Protect the water supplyiii.

Used in combination with well screens in unconsolidated formationsiv.

List reasons for installing casing when drilling water wells with cable tool rigs?b.

Question 88.

Midterm 1: 1-21 (except 12), 45-56

Drilling Review QuestionsOctober 13, 2015 10:25 PM

Drilling and Wells

Well screen is tied or screwed into the bottom of the well casing and lowered into the borehole1)Used in combination with well screens in unconsolidated formationsiv.

The loss of the whole drilling fluida.Loss of drilling fluid through large formation openingsb.

Permeability of formationi.Overbalance in pressureii.

Requires two things:c.

Outline the occurrence of lost circulation.9.

The loss of the water through small formation openings (pores)i.Drilling Fluid Filtrate Lossa.

The loss of the whole drilling fluid through large formation openingsi.Lost Circulationb.

What is the difference between drilling fluid filtrate loss and lost circulation?10.

Increase Viscosity - Bentonitea.

"Barite, which has a specific gravity of 4.2 to 4.35, is a standard weighting material and is much heavier than clay additives and most formation materials (which have specific gravities of 2.6 to 2.7)." (Pg. 299)

i.Weighting Agent in Muds - Bariteb.

What material is commonly used to increase viscosity in drilling muds? What is a common weighting agent in drilling muds?

11.

Consider a hole profile having three hole sections: DC/OH, DP/OH, & DP/Casing. In which hole sections is annular velocity an important consideration and why?

12.

"When drilling in unconsolidated formations, pipe or casing must follow the drill bit closely to prevent caving and to keep the borehole open… The casing sometimes is jacked (pushed into the ground by hydraulic jacks) as drilling and bailing proceeds. Drilling proceeds because it is not necessary to stop to drive pipe." (Pg. 277)

a.How is an open hole maintained in unconsolidated material when drilling with cable-tool method?13.

The pressure exerted by the drilling fluid at depth is greater than the pressure exerted by the formation. This pressure exerted by the drilling fluid is what keeps an open hole while drilling in an unconsolidated formation.

i.Down hole pressure controla.

How do water base drilling fluids maintain an open hole when drilling in unconsolidated material?14.

Formation Permeability Existsa.The pore pressure exceeds the borehole hydrostatic pressureb.

What two down hole conditions are necessary for a well to flow with the pump off?15.

Thrust & Feed - A constant force applied to the bit so it can penetrate the formation. The bit is fed forward as cuttings are removed by a flushing fluid.

a.

Rotation - Functions to expose new material to the bit. Contributes to fragment production in low compressive strength plastic material.

b.

Flushing - A flushing fluid conducts loose material away from the bit and to the surface through the annulus. There are two forms of flushing fluids: air based and water based.

c.

Outline the three requirements for hydraulic rotary drilling with a one or two line summary statement for each.16.

The drill collar provides all FOBi.Applied weight on the drill stringa.

Making use of the weight of the drilling rig itself1)Pull down chainsi.

Hydraulic Pull downii.

Applied force from the ground surfaceb.

What are the two possible sources of thrust (force on bit or weight on bit) in rotary drilling?17.

The drilling fluid must clean the bit face adequately and immediately or the ROP will decrease because the bit won't be as efficient due to it having to re-grind the material it is working. If new material isn't introduced to the bit face the ROP drops dramatically.

a.

What is the consequence of the drilling fluid not cleaning the bit face adequately and immediately as rock fragments are produced?

18.

Air-Based - Dry air, mist, foam, & stiff foama.

Most widely used water-based drilling fluidi.Water-Based - Bentonite Drilling fluidb.

What are two broad groups of drilling fluids commonly used? Name types of fluids within each of these categories.

19.

Under what circumstances might air be the preferred flushing fluid? When is drilling mud the favoured drilling 20.

Drilling and Wells

Air-Based is favoured when in consolidated & semi consolidated rock where relatively low quantities of water are encountered

a.

Mainly used when down hole pressure control is a requirementi.

Drilling mud is favoured when in unconsolidated or unstable formations. It also is able to control formation water.

b.

Under what circumstances might air be the preferred flushing fluid? When is drilling mud the favoured drilling fluid to use?

20.

American Petroleum Institutei.APIa.

The space between the drill string or casing and the wall of the borehole or outer casingi.Annulusb.

Hydrostatic pressure starts at the water table1)The pressure exerted by the formation pore fluidsi.

Pore/Formation Pressurec.

The suspended solids that are deposited on a porous medium during the process of filtrationi.

Gold balls, large bentonite, gravel, hay, sawdust, walnut shells, cotton shells□You cannot continue to drill as is; stopping to add a lost circulation material is required

Minimizes any fluid loss or lost circulation

Uses lost circulation material

A thin, tough, impermeable layer that forms on the borehole wall

Permeability of Formation1.Overbalance in pressure2.

Requires two things

Initial spurt loss followed by suspended solids getting filtered out

Filter Caked.

The pressure at depth expressed in terms of the drilling fluid densityi.Equivalent Drilling Fluid Densitye.

Done to stimulate oil & gas wells for greater production capabilitiesa)Fluid acts as a wedge between grains; forces them apart1)

Hydraulic pressure needed to fracture the formationi.Formation Fracture Pressuref.

Changing out the drill bit. Ie "Tripping the bit"i.The time the drill string spends travelling up and down the boreholeii.

Tripg.

The connections are made using the tongs after the removal of the kelly and the rotary table. 1)

Making connections between drill pipe and drill pipe, drill pipe and drill collar, drill collar and drill bit, etc.

i.Connectionh.

Define and/or illustrate the following:21.

Drilling and Wells

The connections are made using the tongs after the removal of the kelly and the rotary table. 1)

Deform = change in materials shape or volume1)Force/unit area needed to deform a materiali.

Rock Compressive Strengthi.

Pressure exerted by a column of fluid at depthi. ii.

Hydrostatic Pressurej.

Sand or gravel that is smooth, uniform, clean, well-rounded and siliceous. The pack material is placed in the annulus of the well between the borehole wall and the well screen to prevent formation material from entering the screen. Used when formation particles are too small to naturally develop the well.

i.Sand/Gravel Packk.

A filtering device used to keep sediment from entering a welli.Well Screenl.

Less chip hold down which results in the bit not having to re-grind bedrock materiali.Drilling with a negative pressure differential between the formation & boreholeii.

Fast ROP□

Drilling in overburden1.Hydrostatic pore pressure increases the tendency of the borehole to collapse2.

Unstable Boreholesi.

Little control over formation waterii.

Two Drawbacks:□

What is the primary advantage to use of air as flushing fluid? Name 2 drawbacks to use of air.22.

Viscosity & gel strength: Important for the proper function of cuttings removal, to suspend cuttings while the circulation is stopped, and for drilling fluid hydraulics control.

a.

Water loss/filtration control: Important in order to protect the producing zone and improve well development. In order to achieve this an impervious filter cake is required.

b.

Mud density control: To stabilize boreholes and control formation pressures and to maximize ROP.c.

List the 3 major categories of drilling mud control. Outline the importance of each in a 1-2 line summary statement.

23.

Unbalanced, negative surface charges□Mechanical shearing forces if the fluid is mixed or pumped □

Particle separation is further enhanced by:

Particle separation (dispersion) by hydration, electrical and shear forces contributes to the development of a stable, viscous suspension. When bentonite is exposed to water, strong hydration forces pry apart individual layers

a.

Water hydration - water is not free to flow, causing an increase in viscosity

Water becomes tightly bound □Results in greater frictional resistance to flow

Higher viscosity results from higher total particle surface area and less available "free" water○


The degree to which dispersion occurs depends on the type and amount of cations in the interlayer cation cloud

○

Outline the chemical makeup and structure of sodium montmorillonite with the help of the handout illustrating the bentonite particle. How does the nature of this clay enhance its ability to establish a stable, viscous suspension in fresh water so that it is useful as a drilling fluid additive?

24.

Drilling and Wells


The degree to which dispersion occurs depends on the type & amount of cations in the cloud

Low gravity, non-reactive solids exert a poor influence on fluid properties. They contribute to excessive viscosity and density, poor sampling, thick permeable filter cakes, and formation damage.

a.

They don't respond to a changing chemical environmentb.Made up of drilled solids like sandstone/sand, siltstone & silt, limestone, some shales and clays, and crystalline rocks

c.

Why are low gravity, nonreactive solids generally removed from a mud system?25.

"Polymer drilling fluids lack gel strength and cannot keep heavy minerals in suspension at low up hole velocities or when at rest. Soluble salts such as sodium chloride (NaCl) and calcium chloride ( are useful for weighting some drilling fluids that are made with polymeric additives." (Page 299)

a.

Why is barite not used to increase the density of polymer drilling fluids? What is used to increase the density of polymer drilling fluids?

26.

With an elevated pH it dissociates into

SAAP acts as a deflocculant to reduce high viscosities due to high yield point and to control high gel strengths and filtration rates. Excess sodium ion in solution drives the following cation exchange reaction to the right causing flocculating cations on clay particle surfaces, commonly divalent cations such as to be displaced into solution

SAPP - ◊

Caustic soda is added to raise pH and to establish alkalinity in the forms of and . Chemical

treatment is more effective under these conditions and it assists in precipitating flocculating cations.

IAP = Product of the activities of reaction products–

Saturation index =

Elevating by deprotonation of meaning the IAP will be greater than 1 causing Calcite to

precipitate out.–

Caustic Soda (NaOH)◊

Hydrated lime may also be added to raise pH and convert alkalinity into favourable forms. Flocculating cations are more easily precipitated as a consequence.

Conversion of

@ high pH–

Calcium is added, which is the ion we want to precipitate out

Common ion effect–

Two things are happening:

Increases carbonate, facilitating precipitation of –

Hydrated Lime ( ◊

Soda ash addition can also raise pH but it is less effective than caustic soda or hydrated lime in doing so. However, it is effective in dealing with noncarbonate hardness; ie., hardness contributed by noncarbonated minerals such as anhydrite.

Soda Ash ( ◊

Lime removes carbonate hardness

Soda removes non-carbonate hardness

Lime-Soda Softener◊

The marsh funnel viscosity has suddenly increased dramatically. You notice the appearance of anhydrite in the drill cuttings. What is the proper mud treatment to bring viscosity back under control?

27.

Describe the flow behaviour of Newtonian fluids. For illustration, include the shear stress-shear rate relationship for this fluid type and the laminar flow velocity profile in cylindrical pipes.

28.

Drilling and Wells

"A fluid (such as water) that deforms proportionately to an applied stress (or force) is called a Newtonian fluid… Drilling fluids become Newtonian when the yield point has been reached. Beyond the yield point, the relationship between stress and strain is more or less constant, indicating that the viscosity does not change significantly with increasing stress." (Page 306)

a.

Ie. Some definite force has to be applied to initiate flow after which there is a constant rate of increase in shear stress with increasing shear rate

Bentonite fluids behave in a plastic fashion○

Describe the Bingham model of fluid behaviour. Compare the flow behaviour of this type of fluid with that of Newtonian fluids using figures equivalent to those in question 50 to help. What accounts for the difference in flow behaviour between the 2 types of fluids as far as bentonite fluids are concerned? How does the Bingham model relate to the mud properties derived from the Fann viscometer?

29.

Bentonite fluid behaviour: "The gel structure of a drilling fluid made with clay additives is produced when the clay platelets align themselves to join together. The positively charged edge of a plate aligns itself with the negatively charged flat surface of an adjacent plate; this process is called flocculation. This structure gives the liquid a plastic (quasisolid) form with strength properties called gel strength. If enough stress

○

Drilling and Wells

gives the liquid a plastic (quasisolid) form with strength properties called gel strength. If enough stress (force) is applied to the drilling fluid by the pump, then the gel breaks down." (Page 307)

□

□

The slope of the curve on the Bingham model graph equals the plastic viscosity, which can be derived from the PV equation using dial readings from the fann viscometer

□

From the Fann Viscometer:○

The addition of barite will increase the mechanical friction of the bentonite drilling fluid which will increase the shear stress/shear rate ratio. This increase will effect both the Yield Point and Plastic Viscosity readings on the fann viscometer.

a.What affect would the addition of barite have on the Fann apparent viscosity and plastic viscosity?30.

A shear thinning fluid shears thin such that viscosity lessens with increasing shear rate under conditions of laminar flow. The shear stress/shear rate ratio decreases with increasing shear rate.

a.

The advantages of using a shear thinning fluid are apparent in the borehole. In sections of the borehole where the velocity of the fluid slows down due to increasing annular space the viscosity increases allowing the drill fluid to continue to carry drilled solids up the borehole. When pumping ceases for various reasons the viscosity increases even more allowing the drilled solids to be held in place until the pump is turned back on. This advantage allows the drillers to make connections without having to clean the borehole of drilling fluid first.

b.

What is a shear thinning drilling fluid? What are the advantages to use of a shear thinning fluid?31.

Depth = 1000fta.Fluid Density = 9.2ppgb.Annular pressure loss = 15psic.What is the ECD?d.

Given the following:32.

Density = 9.75 lb/gala.$ Solids by weight = 20%b.

Using the appropriate chart, approximate the amount of bentonite required to make 20 centipoise mud with 75 barrels of mix water? What will be the expected mud density, percent solids by weight and percent solids by volume of the mud once prepared?

33.

Drilling and Wells

$ Solids by weight = 20%b.% solids by volume = 9.5%c.85lb/bbl * 75 bbl = 6375lb of Bentonite d.

Describes the flow behaviour of fluids that behave in a pseudo-plastic fashion such as polymer drilling fluidsa.The power index indicates the degree of non-Newtonian behaviour and how shear thinning the fluid is○

N = 1 for Newtonian fluids□How are Newtonian fluids accommodated by this model?○

Finally, illustrate the effect of differing values of 'n' on the laminar profile in cylindrical pipes○

Describe the Power Law model of fluid behaviour. Include a typical curve describing the relationship between shear stress and shear rate for a fluid that is conductive to the Power Law model. How are Newtonian fluids accommodated by this model? Finally, illustrate the effect of differing values of 'n' on the laminar profile in cylindrical pipes.

34.

Determines if viscosity is in range in arbitrary, relative terms (s/L or s/qt)a.Determines if viscosity has changedb.

What are 2 useful pieces of information about drilling fluids that can be obtained from use of the Marsh funnel?35.

What is plastic viscosity? What fluid interactions contribute to drilling fluid plastic viscosity? What is done practically to reduce excessive plastic viscosity? List 3 devices and/or methods that are used to accomplish this.

36.

Drilling and Wells

That part of overall viscosity due to mechanical friction effectsa.

Shale shaker - change to a finer screen–

Desander/desilter –

Worst case scenario dilute with water–

Perform solids control procedures

High PV = Treat the fluid mechanically to reduce non-reactive solids (drill solids)◊

practically to reduce excessive plastic viscosity? List 3 devices and/or methods that are used to accomplish this.

Yield Point: That part of overall viscosity due to electrical friction effects of bentonitea.Gel Strength: "A measure of the ability of a colloidal dispersion to develop and retain a gel form, based on its resistance to shear."

b.

"However, the major difference between YP and gel strength in term of hydraulics is that gel strength will not exist once the fluid is moving and the gel has been broken, while the effects of YP will not disappear when the fluid is moving." http://www.drillingcontractor.org/understanding-yield-point-effect-on-pressure-surges-critical-to-managing-deep-difficult-mpd-wells-1933

c.

Temperature and Pressure will contribute to a high Yield Point and a high Gel Strengthd.

What is the difference between yield point and gel strength? What are 2 factors that contribute to high YP and gel strength?

37.

The use of the Reynolds number pertaining to hydraulics: "The Reynold's number is a dimensionless number that is a ratio of inertial forces to viscous forces. For groundwater flow, the Reynold's number relates the characteristic dimension of the flow space and the velocity, density, and viscosity of a moving fluid to determine whether laminar or turbulent flow exists." (Page 25)

a.

At higher p (fluid density), higher D (diameter) = lower Critical Velocity to transition to turbulent flow

At higher = Higher critical velocity required to transition to turbulent flow

What is the use of Reynold's number pertaining to hydraulics? What is the effect of fluid density, velocity and viscosity and the influence of hydraulic diameter on the existence of laminar or turbulent flow conditions?

38.

N = Power law index1.Nre = 3470-1370ni.

ii. iii.As shown above, the Reynolds number increases with each decrease in the Power Law 'n' value. This means that the velocity would have to be greater to induce turbulent flow for each decrease in power law 'n' value.

iv.

Decreasing Power Law 'n' value = a.

What is the effect of decreasing Power Law 'n' values on the Reynold's number for non-Newtonian fluids? What does this mean regarding the velocity required to achieve turbulent flow with increasing non-Newtonian behaviour?

39.

"A chaotic flow pattern at higher flow velocities in which case frictional shear at the fluid layer interfaces causes the orderly laminated structure to break down, resulting in a flat velocity profile."

i.

Turbulent Flow: "Water flow in which the flow lines are confused and heterogeneously mixed. It is a typical flow in surface-water bodies." (Page 772)

a.

"Orderly flow pattern where fluid layers flow past one another."i.

Laminar Flow: Water flow in which the stream lines remain distinct and the flow direction at every point remains unchanged over time. It is characteristic of the movement of ground water. (Page 766)

b.

Friction pressure loss is the energy loss required to drive a fluid from A to B.i.How does the flow regime affect the required pressure losses associated with fluid movement?c.

Compare conditions under laminar and turbulent flow regimes. Sketch the velocity profile in cylindrical pipes for each case. How does the flow regime affect the required pressure losses associated with fluid movement?

40.

Drilling and Wells

http://www.drillingcontractor.org/understanding-yield-point-effect-on-pressure-surges-critical-to-managing-deep-difficult-mpd-wells-1933

http://www.drillingcontractor.org/understanding-yield-point-effect-on-pressure-surges-critical-to-managing-deep-difficult-mpd-wells-1933

Friction pressure loss increases dramatically when a fluid goes from laminar flow to turbulent flow.i.

Drilling and Wells

Smaller the ion the greater tendency for adsorption

Cation size1.

Ex. □Higher the charge the greater tendency for adsorption

Cation charge2.

Increase concentration high enough and it will counteract any effects of charge & size

Concentration in solution vs. that adsorbed (mass action)3.

List 3 factors that affect the process of cation exchange. In what manner does each factor affect the reaction?41.

Deflocculant - Dispersion of particles that were once flocculateda.SAAP acts as a deflocculant to reduce high viscosities due to high yield point and to control high gel strengths and filtration rates. Excess sodium ion in solution drives the following cation exchange reaction to

b.

How does SAPP work as a drilling mud thinner?42.

Drilling and Wells

strengths and filtration rates. Excess sodium ion in solution drives the following cation exchange reaction to the right causing flocculating cations on clay particle surfaces, commonly divalent cations such as to be displaced into solutionSAPP = c.

Soda Ash a.Caustic Soda (NaOH)b.Hydrated Lime ( c.

Name 3 chemicals used for pH control of bentonite drilling fluids.43.

A fluid with a gel structurei."If a drilling fluid with clay additives is left standing in a borehole or mud pit, over time its gel strength increases as more clay plates align themselves. This quality is called Thixotropy." (Pg. 309)

ii.

Thixotropic fluida.

Extremely small solid particles, 0.0001 to 1 micron in size, which do not settle out of a solution; intermediate between a true dissolved particle and a suspended solid which does settle out of a solution.

i.Colloidb.

A tangled mass that creates mechanical frictional shear stress (viscosity) under flowi.Stable suspensionc.

Particles will adhere when they collide and settle out resulting in unstable suspensioni.Unstable suspensiond.

Ion exchange process in which cations in solution are exchanged for other cations from an ion exchanger.

i.Cation exchange e.

Isomorphous Substitution = a change in chemistry but not structurei.Isomorphous substitutionf.

"A sudden increase in the rate of penetration during drilling. When this increase is significant (two or more times the normal speed, depending on local conditions), it may indicate a formation change, a change in the pore pressure of the formation fluids, or both."

i.Drill breakg.

A dimensionless number that is a ratio of inertial forces to viscous forcesi.Reynold's numberh.

Flow velocity below which flow is laminar and above which flow is turbulenti.Critical velocityi.

The velocity at which one layer slides past another at some known distancei.Shear ratej.

Resistance of a fluid to flow. This resistance acts against the motion of any solid object through the fluid and also against motion of the fluid itself past stationary obstacles. Viscosity also acts internally on the fluid between slower and faster moving adjacent layers. All fluids exhibit viscosity to some degree. It is optically recognized as thickness.

i.Viscosityk.

Particle arrangement in the non-hydrated state1.Can be caused by excess flocculating cations ( ) in solution2.

Face-face arrangementi.Clay aggregationl.

Reduction in electrical repelling and hydration forces (flocculating cations)i)Crowding of particlesii)Decreasing shear/mechanical forcesiii)

Caused by:a)Results in a dramatic increase in viscosity1.

Edge-edge, edge-face arrangementi.Clay Flocculationm.

Result of hydration, electrical, and shear forces1.Complete separation of particlesi.

Clay dispersionn.

Shear stress/shear rate ratio for a given shear ratei.Effective viscosityo.

The component of stress that acts tangential to a plane through any given point in a bodyi.The internal resistance to flow from the friction force of fluid layers sliding past one anotherii.

Shear stressp.

Define the following:44.

Drilling and Wells

The internal resistance to flow from the friction force of fluid layers sliding past one anotherii.

Pressure on a fluid that is lost by frictional effects as it flows from one point to another in a flow system

i.Friction pressure lossq.

Suitable for unconsolidated (low compressive strength) formations. Drilling requires both thrusting (bit penetration) and shearing action (fragment production). These bits are inexpensive and easily replaced (financially).

a.

Describe the use and operation of drag bits. How is bit penetration and fragment production achieved with this bit type?

45.

The cutting structure for a high strength, abrasive, crystalline rock is many closely spaced small diamonds. The operation requires high RPM and low FOB in order to shear the formation. Small diamond dimples make up the cutting surface of the PDC bit. A high FOB would just knock the diamonds off the bit.

a.

What is the configuration of the cutting structure of a diamond bit designed for use in tough, abrasive, high compressive strength rock? In general terms, what is the operation of these bits?

46.

Low RPM cuts back on the torquea)High FOB, low RPM1.

Lower strength formations: larger, longer, widely spaced teethi.

Shearing the formationa)High RPM, low FOB1.

High strength, abrasive, crystalline rock: many closely space small diamondsii.

Tooth size, shape, and spacing is manipulated along with bit operation to accommodate different formation types.

a.

How is diamond bit configuration and operation manipulated to suit drilling in rocks having different compressive strengths?

47.

"Rotation of the bit helps to ensure even penetration and straighter holes-including when drilling in extremely abrasive or resistant rock types." (Page 264)

a.Why does drilling with hammer bits generally result in less hole deviation?48.

Teeth: long, slender, widely-spaced, mill tooth or tungsten carbidei.Cone geometry: high cone effectii.Bit operation: high RPM, low FOBiii.Drilling action: Shearingiv.

Low compressive strength, plastic formations:a.

Teeth: numerous, closely spaced, short, blunt teeth, tungsten carbidei.Cone geometry: little to no offsetii.Bit operation: high FOB, low RPMiii.Drilling action: Crushingiv.

High compressive strength, brittle, abrasive formationsb.

How does rock bit cutting structure design and rock bit operation differ for rocks having different abrasiveness and compressive strength?

49.

Low compressive strength, plastic material: Shearinga.High compressive strength, brittle rock: Crushing b.

What is the drilling action of a rock bit for use in low compressive strength, plastic material? What is the drilling action of a rock bit for use in a high compressive strength, brittle rock?

50.

Allow cones to rotatei.Support thrust loadsii.

Two functions of rock bearings:a.

Not sealed - lubricated by drill fluid and susceptible to grit of drill cuttings1.Used on cheap, inexpensive bits2.

Ball & Rolleri.

Not susceptible to grit from drill cuttings1.Much more expensive than non-sealed bearings2.

Sealed & lubricatedii.

Two types of rock bit bearings:b.

What are 2 functions of rock bit bearings? What are 2 types of rock bit bearings?51.

Cone offseta.Tooth length & spacingb.Gaugec.

What are the 3 aspects of bit performance?52.

517a.What is the IADC code for a Hughes J22 rock bit?53.

Drilling and Wells

517a.

646a.

What is the IADC code for a tungsten carbide rock bit with journal bearings that is conductive to drilling in medium hard formations of high compressive strength?

54.

The time it takes to trip the bit is expensive so maximizing time in the borehole is more important than maximum ROP.

a.Why is it more important to select a durable bit in deep holes than to select one that maximizes ROP?55.

T3 = 3/8 of the tooth bit is missinga.B2 = 2/8 of bearing life usedb.G.125 = .125 inches under gaugedc.

A used tungsten carbide bit is given the following evaluation: T3, B2, G.125. What is meant by this?56.

Bit cost: $5,000a.Rotation time: 12b.Trip time: 4.0 hoursc.Footage: 250d.Rip Operating Cost: $500/houre.

What is the cost per foot for the following bit run?57.

Drill collar provides all FOBi.Stability to the bitii.Straight hole with less deviationiii.

Large Diameter, thick walled pipe.a.What are drill collars? Outline 3 functions of drill collars using a 1 or 2 line summary for each.58.

Having stabilizers on the drill collar will tend to keep the borehole going in the same directiona.What is the purpose of a drill string stabilizer?59.

Influenced by weight of pendulum & length of penduluma.What are the 2 factors that influence the pendulum effect?60.

Decreasing the number of stabilizers on the drill collar increases the length of the penduluma.

Coupled with decreasing the FOB the borehole will straighten itself outb.

If it is perceived that the hole is deviating too quickly, what can be done with the FOB/RPM combination to minimize this problem? Why does this work?

61.

Casing installationa.Groutingb.Filter pack installationc.Vertical turbine pump settingd.Wear on drill string/casinge.Stuck drill stemf.

List 6 operational difficulties that can arise as a result of hole alignment and deviation problems?62.

List 3 categories of reasons why holes can become crooked or out of plumb? Define each of these.63.

Boulders: deflect bits, casinga.

<45 degree, holes drill up (notes 74)i.>45 degree, tend to drill down dip (notes 74)ii.

Inclined Strata b.

Drill collarsi.Stabilizers: lack of stabilizationii.

Poor bit stabilizationc.

Increased compression of the drill biti.Insufficient stabilization; lessened with increasing stabilizationii.

Excessive FOBd.

If it is not perfectly straight it will deviatei.Important to use casing clamps when welding casing pieces togetherii.

Trueness of casing or drill pipee.

Application of pull down can cause this shifting1.Over drilling time the rig is constantly being shiftedi.

Drilling rig off levelf.

List 5 factors that may cause hole deviation.64.

Desired maximum FOB = 25,000lbsa.Mud density = 11.5ppgb.Drill collars: 7.0 inches OD, 2.25 inches ID, 117.1 pounds per foot, average length = 31.24 feetc.

Given the following:65.

Drilling and Wells

Drill collars: 7.0 inches OD, 2.25 inches ID, 117.1 pounds per foot, average length = 31.24 feetc.What is the required number of drill collars? Include a 20% safety factor.d.

"Pendulum effect is the effect which tends to bring the drill bit along with the active string to the lower side of hole."

i.Pendulum effecta.

a)

Drill string stabilizerb.

"Is the measurement of a straight line perpendicularly downwards from a horizontal plane."i.True vertical depthc.

Straight holed."Is the measurement of a straight line perpendicularly downwards from a horizontal plane."e.

Boreholes commonly deviate from plumbness and alignmenti.2/3 the well inside diameter (inches) per 100 feet of pump setting depth (AWWA)ii.1 degree per 50 feet (EPA)iii.

Hole deviationf.

Must be in the drill collar; if it is above the drill collar the drill pipe will flex back and forth causing it to break off

i.Drill string neutral pointg.

Commonly used in the water well and monitoring well industries1.

Keeps the casing perfectly centered in the boreholei.Centralizerh.

More offset =more shearing1.Cone centerlines are offset in the direction of bit rotationi.

Rock bit cone offseti.

Series (cone offset)1.Type (Tooth length, spacing)2.

Gauge protectiona)Bearingsb)

Features3.

Three digit code to assist in rock bit selection for drilling in various formation typesi.IADC codej.

Define and/or illustrate the following:66.

Drilling and Wells

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