Drilling Engineering 1 Course (2nd Ed.)

1. Drillstring TubularsA. Drill Pipes

a. properties of drill pipes

B. Drill Pipe Elevator

C. Drill Collars & Heavy Wall Drill Pipes

1. Drillstring EquipmentA. Special Tools

2. Connections; Make–up and Break–out

3. Other Drillstring Equipment

Drillstring equipment

Several drilling equipment are used in the drillstring.

The most important are:stabilizers,

provide localized additional support points (localized larger diameter) in one or more positions along the drillstring.

reamers,

hole–openers.

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Advantages of drillstring

For vertical wells, the stabilizer prevents low frequency vibration in the drillstring during rotation.

The advantages are:reduce wear (of both drillstring and casing),

reduce mechanical fatigue,

reduce mechanical instability of formation (caving),

reduce tortuous hole.

Stabilizers are essential equipment for directional drilling.

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Stabilizer special characteristics and typesSuitable choice of

number and position of stabilizers in the drillstring lend to the bottom hole assembly (BHA, the lower part of

the drillstring composed of drill collars, stabilizers and HWDP)

special characteristics in terms of inclination control:angle build–up,

angle drop–off,angle hold.

Stabilizer may be of the following types:integral blade,interchangeable blade,non–rotating blades,replaceable blades,clamp–onnear-bit,

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The diameter of stabilizers

The diameter of stabilizers can be in gauge or under gauge.

More recently, remote adjustable blade stabilizers were introduced. Changing suitably the diameter of the stabilizers provide

a level of control in the directional behavior of BHAs.

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Some Stabilizers

(a) integral,

(b) interchangea

ble,

(c) non–

rotating,

(d)replaceable

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Reamers

The purpose of the reamer is to keep the diameter of the open hole in gauge, that is, with the expected original diameter of the bit.

Two reasons may cause a decrease in the original diameter: formation swelling (hydrated shales,

moving salt),bit diameter reduction (hard and

abrasive formations).

The reamer also functions as a stabilizer since the rollers touch the borehole wall.

Different types of rollers can be selected to suit the formations being reamed.

A roller reamerSpring14 H. AlamiNia Drilling Engineering 1 Course (2nd Ed.) 10

The hole–opener

The hole–opener is a tool designed to enlarge the diameter of a previously (or simultaneously drilled smaller borehole. Three situations (at least) are possible: to drill the borehole section with a smaller bit,

and later to enlarge to the final diameter (a special tool called bull nose is connected in the place of the bit, to guide the hole opener along the pre-drilled hole),

to drill the borehole section with a smaller bit and simultaneously enlarge to the final diameter,

to enlarge a section below a casing with a diameter larger than the internal diameter of the casing. In this case, a special hole opener (also caller

underreamer) with hinged arms actuated hydraulically is used (the drilling fluid pressure actuates in rams that open the arms forcing the cutters against the borehole wall).

A fixed hole–openerSpring14 H. AlamiNia Drilling Engineering 1 Course (2nd Ed.) 11

manual tongs

To make–up and break–out the pipe connections (during normal operations and drillstring trips), big self–locking wrenches called manual tongs are used to grip the drillstring and apply torque. The tongs are kept suspended at suitable height

above the rotary table (3 to 5ft) balanced by counter–weights.

They work in pairs, one turns to left (counterclockwise) and the other to right (clockwise).

They are mechanically or pneumatically actuated by the cathead (special rotating spools connected to the drawworks).

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Manual tongs.

Left tongue (break-out). Right tong (make–up).Spring14 H. AlamiNia Drilling Engineering 1 Course (2nd Ed.) 14

make–up and break–out

To make–up a connection, the left tong

grips the upper tool joint (box) of the lower pipe,

and the right tong grips the lower tool joint (pin) of the upper pipe.

The left tong is connected by a steel rope to a fixed point in the derrick,

and the right tong is connected to the cathead (turns the upper pipe).

To break a connection, the left tong

grips the lower tool joint (pin) of the upper pipe,

and the right tong grips the upper tool joint (box) of the lower pipe.

The right tong is connected by a steel rope

to a fixed point in the derrick,

and the left tong is connected to the cathead

(also turns the upper pipe).

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Technical notes about tongs

When set and ready to apply torque, the angle between the arms of the tongs

should be either 90 or 180 (the ideal is zero degrees but operational difficulties make this position not practical).

It is important to leave the rotary table unlocked, to avoid damage to the pipe caused by the slips.

Compressed air tongs or spinners are also used to speed–up the operation,

but the torque to make–up or to break–out the connection is always done using the manual tongs.

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Compressed air tongs (spinners) & Tongs

A spinner Tongs in position to make–up a connectionSpring14 H. AlamiNia Drilling Engineering 1 Course (2nd Ed.) 17

The angle between the arms of the tongsTo make–up or

break–out a connection, the drillstring

must be resting on the master bushing using the slips (DP and HWDP) or slips+safety clamp (DC and any other slick equipment.)

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Make–up Torque

It is very important to apply the right torque during the make–up of a connection. Too little torque

will not provide a suitable seal between the pin and box shoulders, and leakage might wash out the threads causing failure of the connection.

Too much torque may cause mechanical failure of the threads, either in the box or in the pin.

The API RP7G tables present the maximum (tb.9) and minimum (tb.10) torques for each standard connection.

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Drill Bit

The bit is connected to the lower end of the drill collars. Bits are manufactured with a pin, so that to connect

to the lower pin of the drillstring, a bit sub is used. The bit sub is a short sub (11/2 to 2 ft) with two box connections.

There are a large variety of bits. Each type is designed to drill rocks of different hardness,

composition, abrasiveness, etc, encountered during drilling operations.

It is a duty of the drilling engineer to select the most appropriate bit and the drilling parameters

(nozzle sizes, weight-on-bit, rotation speed, and flow rate)

to optimize the performance of the operation.

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Other Drillstring Equipment

In addition to the kelly–rotary table assembly, two other methods can be used to promote rotation to the bit:Top drive,

Bottom hole motors (positive displacement motors and turbines).

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top drive

The top drive, also called power swivel, takes the place of the kelly, and the torque is applied to

the top of the drill pipe section by mean of hydraulic or electric motors.

The assembly slides along tracks (most models incorporate a swivel in the design,) and is suspended by the hook.

The reactive torque is transmitted to the rig structure directly through the tracks or by a torque reaction beam.

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advantage of using a top drive

A great advantage of using a top drive is the possibility to drill a full

stand (3 or 4 drill pipes) without interruption, saving time in connections.

Another advantage is the possibility of rotating

the drillstring during the trips reducing the drag to pull–out or slack–off the drillstring in the hole for high inclination drilling.

An electrical top driveSpring14 H. AlamiNia Drilling Engineering 1 Course (2nd Ed.) 25

Bottom hole motors and Turbines

Bottom hole motors are special engines located above the bit

to promote bit rotation.

convert hydraulic power of the drilling fluid (P = q ∆p) into mechanical (rotational) power.

Turbines use fluid momentum conversion on the blades of

stator/rotor to generate rotation and torque.

operates in high speed and has a narrow range of operation. The torque decreases steadily from the maximum at 0 rpm

(stalled) to zero at the maximum speed.

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A bottom hole turbine

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Positive displacement motors

Positive displacement motors (PDM) use continuous displacement of constant volume

compartments created between an elastomer stator and a steel rotor to generate rotation and torque. The rotation speed of a PDM is function of the flow rate, and

the torque is directed related to the pressure differential across the motor (easily monitored from the surface).

The use of bottom hole motors is essential for directional drilling.

The use of bent sub or bent housing provides a good deal of control of the inclination and the

azimuth, allowing to drill complex trajectories.

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A bottom hole PDM

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1. Jorge H.B. Sampaio Jr. “Drilling Engineering Fundamentals.” Master of Petroleum Engineering. Curtin University of Technology, 2007. Chapter 3

1. Hydraulic IntroductionA. Hydrostatic Pressure

a. Calculation for Incompressible Fluids

b. Calculation for Compressible Fluids

c. Buoyancy

B. Drillstring Designa. Length of Drill Collars; Neutral Point Calculation