Post on 08-Nov-2014
description
1Formation Pressure Evaluation School
04/08/23
Baker Hughes INTEQ
Surface Logging Systems
WELCOME!!To The FORMATION PRESSURE
EVALUATION COURSE
5 Fun Filled Days with Exam!
Formation Pressure
04/08/23 Formation Pressure Evaluation School
2
Formation Pressure
Course Objectives ...1. To COMMUNICATE.
2. To collect DATA.
3. To recognise TRENDS.
4. To evaluate PRESSURE.
5. And ...
... develop a plan to be
able to undertake pressure
evaluation anywhere!
04/08/23 Formation Pressure Evaluation School
3
Day One :
• Introduction• Communication• Basic Terminology• Hydrostatic & ECD• Overburden
Day Two :
• What is Pore Pressure? • Origins of Abnormal Pressure• Pressure Evaluation
Day Three :
• Fracture Pressure Gradient
• Casing Seat Placement• Basic Well Control
Course Outline
Day Four :
• Predict Exercise
Day Five:
• Final Exam
Formation Pressure
04/08/23 Formation Pressure Evaluation School
4
Day OneObjectives :• Introduction
• The Plan• Communication• Become familiar with
• Basic Terminology• Hydrostatic & ECD• Overburden
Formation Pressure
04/08/23 Formation Pressure Evaluation School
5
INTRODUCTION
Formation Pressure
04/08/23 Formation Pressure Evaluation School
6
The PlanIn the beginning there isa Plan …
… and the Plan is best shown as a flow diagram.
Note: If you learn the flow diagramyou can get through the course very easily and undertake pressure evaluation anywhere! You don’t need a computerjust the ability to undertake a few simple exercises with a calculator!
Formation Pressure
04/08/23 Formation Pressure Evaluation School
7
• Density Logs• Porosity Logs
• Regional Curves• Equations
• Rock Cuttings Density
ROCK BULK DENSITY
b
Overburden Pressure“S” in psi, bars, atm.
Overburden Gradient“S” / TVD from rkb
ThePlan
(1)OverburdenPressure
(Rock Properties)
Formation Pressure
04/08/23 Formation Pressure Evaluation School
8
• Offset Well Data• Rw Catalogues• Resistivity Logs
• Bucket on a Rope
Formation Pressure
PORE WATER DENSITY
f
Normal Hydrostatic Pr.Normal Pore Pressure“P” in psi, bars, atm
ThePlan
(2)PorePressure
(Fluid Properties)
Normal Pore Pr. Gradient(“P” / TVD from water level)
Formation Balance Gradient(“P” / TVD from flowline)
Gas,Dxc,Elogs,Temp.Flows,Kicks,etc.
Estimated PorePressure andFB Gradient
MINIMUMSTATIC MUD
DENSITY
“S”(from 1)
04/08/23 Formation Pressure Evaluation School
9
Formation Pressure
Estimated Fracture Pressure at Any Depth
Maximum Dynamic Mud Pressure &
Maximum Shut-in Casing Pressure
LEAK OFFTEST
Kick Tolerance
“S”(from 1)
“P”(from 2)
Rock CuttingsPoisson’s
Ratio “”
Tectonicstress
ThePlan
(3)FracturePressure
04/08/23 Formation Pressure Evaluation School
10
The PlanThe aim of this Plan and partof the aim of this Course ...
To give employees the knowledgefor drilling safe wellbores in thewindow between
Minimum Static Mud Density and
Maximum Dynamic Mud Pressure
Formation Pressure
04/08/23 Formation Pressure Evaluation School
11
• Abnormal formation pressures occur in most sedimentary basins worldwide.
Introduction
Formation Pressure
04/08/23 Formation Pressure Evaluation School
12
• Abnormal formation pressures occur in most sedimentary basins worldwide.– They occur in all geologic
age formations.
– They occur at all depths.
Introduction
Formation Pressure
04/08/23 Formation Pressure Evaluation School
13
• Abnormal formation pressures occur in most sedimentary basins worldwide.– They occur in all geologic
age formations.
– They occur at all depths.
– A third to a half of all wells drilled experience abnormal pressures.
Introduction
Formation Pressure
04/08/23 Formation Pressure Evaluation School
14
• Understanding formation pressures is important for several reasons
– Minimize drilling costs due to lost time and equipment problems through ...
Introduction
Formation Pressure
04/08/23 Formation Pressure Evaluation School
15
• Understanding formation pressures is important for several reasons
– Minimize drilling costs due to lost time and equipment problems through
• Well kicks and blowouts
CHING!CHING!
Introduction
Formation Pressure
04/08/23 Formation Pressure Evaluation School
16
CHING!CHING!CHING!
• Understanding formation pressures is important for several reasons
– Minimize drilling costs due to lost time and equipment problems through
• Well kicks and blowouts• Stuck pipe
Introduction
Formation Pressure
04/08/23 Formation Pressure Evaluation School
17
• Understanding formation pressures is important for several reasons
– Minimize drilling costs due to lost time and equipment problems through
• Well kicks and blowouts• Stuck pipe• Lost circulation
CHING!CHING!CHING!CHING!
Introduction
Formation Pressure
04/08/23 Formation Pressure Evaluation School
18
• Understanding formation pressures is important for several reasons
– Minimize drilling costs due to lost time and equipment problems through
• Well kicks and blowouts• Stuck pipe• Lost circulation
– Ensure rig personnel safety.– Stop environmental pollution.– Minimize loss of reserves.
Introduction
Formation Pressure
04/08/23 Formation Pressure Evaluation School
19
• The evaluation of formation pressure is critical for well planning and completion.
• When a well is drilled there are several kinds of pressure that must be considered.
Introduction
Formation Pressure
04/08/23 Formation Pressure Evaluation School
20
• The evaluation of formation pressure is critical for well planning and completion.
• When a well is drilled there are several kinds of pressure that must be considered.
– Overburden pressure
Introduction
Formation Pressure
04/08/23 Formation Pressure Evaluation School
21
• The evaluation of formation pressure is critical for well planning and completion.
• When a well is drilled there are several kinds of pressure that must be considered.
– Overburden pressure
– Formation pore pressure
Introduction
Formation Pressure
04/08/23 Formation Pressure Evaluation School
22
• The evaluation of formation pressure is critical for well planning and completion.
• When a well is drilled there are several kinds of pressure that must be considered.
– Overburden pressure
– Formation pore pressure
– Fracture pressure
Introduction
Formation Pressure
04/08/23 Formation Pressure Evaluation School
23
Hydrostatic Pressure = Vertical Depth * Mud Weight * 0.0519
• The evaluation of formation pressure is critical for well planning and completion.
• When a well is drilled there are several kinds of pressure that must be considered.
– Overburden pressure
– Formation pore pressure
– Fracture pressure
– Mud hydrostatic pressure
Introduction
Formation Pressure
04/08/23 Formation Pressure Evaluation School
24
Equivalent Circulating Density (ECD)
• The evaluation of formation pressure is critical for well planning and completion.
• When a well is drilled there are several kinds of pressure that must be considered.
– Overburden pressure
– Formation pore pressure
– Fracture pressure
– Mud hydrostatic pressure
– Equivalent Circulating Density (ECD)
Introduction
Formation Pressure
04/08/23 Formation Pressure Evaluation School
25
• To successfully drill a well to completion, a comprehensive mud and casing program must be made.
Fracture Gradient
PorePressure Gradient
MudWeight
Introduction
Formation Pressure
04/08/23 Formation Pressure Evaluation School
26
• To successfully drill a well to completion, a comprehensive mud and casing program must be made.
• There must be a balance between mud hydrostatic pressure and formation pore pressure.
Introduction
Formation Pressure
04/08/23 Formation Pressure Evaluation School
27
• To successfully drill a well to completion, a comprehensive mud and casing program must be made.
• There must be a balance between mud hydrostatic pressure and formation pore pressure.
• Problems that can occur – Mud hydrostatic < Formation
• Kicks
Introduction
Formation Pressure
04/08/23 Formation Pressure Evaluation School
28
• To successfully drill a well to completion, a comprehensive mud and casing program must be made.
• There must be a balance between mud hydrostatic pressure and formation pore pressure.
• Problems that can occur – Mud hydrostatic < Formation
• Kicks• Stuck Pipe
Introduction
Formation Pressure
04/08/23 Formation Pressure Evaluation School
29
• To successfully drill a well to completion, a comprehensive mud and casing program must be made.
• There must be a balance between mud hydrostatic pressure and formation pore pressure.
• Problems that can occur – Mud hydrostatic < Formation
• Kicks• Stuck Pipe
– Mud hydrostatic > Formation• Lost Circulation
Introduction
Formation Pressure
04/08/23 Formation Pressure Evaluation School
30
COMMUNICATION
Formation Pressure
04/08/23 Formation Pressure Evaluation School
31
Pressure EvaluationWhat Data Will You Be Given To Assist You?
• Hopefully as much as possible!
• When in doubt ask for more!!
• If the Client is serious about having
you perform a high quality pressure
evaluation they should be as helpful
as possible.
You should NOT need a crystal ball ...... yet.
Formation Pressure
04/08/23 Formation Pressure Evaluation School
32
Pressure Evaluation Tools
• Prior to drilling– Surface geophysical– Regional geology– Seismic– Offset data
• While drilling– Drilling parameters - drill rate, torque, dxc, pump pressure etc.– MWD / LWD / PWD - gamma ray, resistivity, sonic, density etc.– Drilling fluid - gas, temperature, pit volume, salinity etc.– Geology - shale density, volume, shape, size, shale factor etc
• After drilling– Wireline logs– Pressure tests– Data analysis
Formation Pressure
04/08/23 Formation Pressure Evaluation School
33
Communication
Who?
Why?
When?
Formation Pressure
04/08/23 Formation Pressure Evaluation School
34
Who and Why?
• Everyone associated with the drilling process ...
– Mudlogger / Geologist ?– Mud Engineer ?– MWD Engineer ?– Driller ?– Derrick Hand / Shaker Hand ?– Company Man / Drilling Engineer ?– Your Relief ?– Your Coordinator ?
Formation Pressure
04/08/23 Formation Pressure Evaluation School
35
When?
• In a timely manner
– There should be constant communication– Communicate when conditions are normal– Communicate when you suspect a problem
And remember to ...
– Never ignore changes in trends– Report everything, but prepare to be wrong– Get second opinions when necessary– Write things down!
Formation Pressure
04/08/23 Formation Pressure Evaluation School
36
TERMINOLOGY
Formation Pressure
04/08/23 Formation Pressure Evaluation School
37
• Hydrostatic Pressure– The pressure exerted at any point in a static fluid column
• Overburden Pressure– Pressure of the weight of overlying sediments and fluids
• Pore Pressure– Pressure exerted by the formation fluids
• Formation Balance Gradient– Mud density needed to balance the pore pressure
• Fracture Pressure– The pressure needed for hydraulic fracturing to occur
Formation Pressure Terminology
Formation Pressure
04/08/23 Formation Pressure Evaluation School
38
• Equivalent Circulating Density – Density of the mud while being pumped
• Pressure Gradients
– pressure divided by TVD & measured in psi/ft or bars/m
• Equivalent Mud Weight or Density
– pressure gradient measured in ppg or gm/cc
– note that gm/cc and specific gravity (sg) are used
interchangeably
psi/ft / 0.052 = ppg bar/m / 0.0981 = sg
Formation Pressure Terminology
Formation Pressure
04/08/23 Formation Pressure Evaluation School
39
Pressure Gradients
Formation Pressure
0 1000 2000 3000 4000 5000 Pressure
Depth
5000
2500
Gas Gradient 0.07 psi/ftOil Gradient 0.30 psi/tfWater Gradient 0.433 psi/ft“Normal” Formation Gradient 0.465 psi/ft10ppg Mud Gradient 0.519 psi/ft15ppg Mud Gradient 0.779 psi/ft21ppg Mud Gradient 1.090 psi/ft
04/08/23 Formation Pressure Evaluation School
40
HYDROSTATIC PRESSURE AND E.C.D.
Formation Pressure
04/08/23 Formation Pressure Evaluation School
41
• The pressure exerted by a static column of fluid
Hyd. Pr. (psi) = TVD (ft) * Fluid Density (ppg) * 0.0519
Hyd. Pr. (bar) = TVD (m) * Fluid Density (sg) * 0.0981
• The hydrostatic pressure gradient will be
Gradient (psi/ft) = Hyd. Pr. (psi) / TVD (ft)
Gradient (bar/m) = Hyd. Pr. (bar) / TVD (m)
Hydrostatic Pressure
True vertical depths should be used in all pressure calculations. Mud depths should be referenced from the flowline.
- psi/ft / 0.0519 = ppg- bar/m / 0.0981 = sg
Formation Pressure
04/08/23 Formation Pressure Evaluation School
42
• The normal hydrostatic pressure of a formation depends solely on the pore water density and the true vertical depth.
• The mud hydrostatic pressure is the pressure exerted at any point by the mud column.
Hydrostatic PressureMud Weight =10.00 lb/gal
Vertical Depth =10,000 ftMeasured Depth=10,000 ft
Hydrostatic Pressure:
MW * TVD * 0.0519
= 5190 psi
Formation Pressure
04/08/23 Formation Pressure Evaluation School
43
• The normal hydrostatic pressure of a formation depends solely on the pore water density and the true vertical depth.
• The mud hydrostatic pressure is the pressure exerted at any point by the mud column.
Hydrostatic Pressure
Hydrostatic Pressure:
MW * TVD * 0.0519
= 3633 psi
Mud Weight =10.00 lb/gal
Vertical Depth =7,000 ftMeasured Depth=10,000 ft
Formation Pressure
04/08/23 Formation Pressure Evaluation School
44
Hydrostatic & Pore Pressure • Normal hydrostatic pressure = Normal pore pressure
• Quite simply pore pressure is the pressure exerted by pore fluids which reflect the water density in the basin of deposition
• Non-marine • Brackish • Open marine • Partially restricted marine or saline • Very restricted marine or hypersaline
Normal pore pressure can be anywhere
between 8.34 ppg and 9.00 ppg
Formation Pressure
04/08/23 Formation Pressure Evaluation School
45
• Balanced Situation : Mud Hydrostatic = Pore Pressure
• see “Minimum Static MW” in the “Plan”
• Underbalanced : Mud Hydrostatic < Pore Pressure
• kicks / sloughing / fast drilling / stuck pipe
• Overbalanced : Mud Hydrostatic > Pore Pressure
• fluid loss / fracturing / slow drilling / stuck pipe
Hydrostatic & Pore Pressure
Formation Pressure
04/08/23 Formation Pressure Evaluation School
46
• Consider that the formation and the annulus form a u-tube.
• To be balanced, both arms need to have the same pressure.
Formation Balance GradientThe U-Tube & J-Tube Effect
Mud Pore Fluid
Mud Hydrostatic = Pore Fluid Hydrostatic
Formation Pressure
04/08/23 Formation Pressure Evaluation School
47
• Most rigs can be considered to be j-tubes.
• The Formation Balance Gradient is the mud weight needed to balance pore fluids when considering the j-tube effect.
Pore Fluid
Mud Hydrostatic = Pore Fluid Hydrostatic
Mud
Flowline
Air Gap
Formation Balance GradientThe U-Tube & J-Tube Effect
Formation Pressure
04/08/23 Formation Pressure Evaluation School
48
Equivalent Circulating Density
• The ECD is the apparent density of the mud while circulating.
• Annular pressure losses due to frictional effects increase the apparent density.
• Annular losses are affected by
– Mud rheology– Hole size & pipe geometry– Flow rate & annular velocity
• The ECD is typically greatest at the bottom of the hole.
Mud Weight =10.00 lb/gal
Circulating mudcreates pressurelosses against the hole wallPressure lossesadd to the mudhydrostatic.ECD is typically greatest at the bottom of the wellbore.
Formation Pressure
04/08/23 Formation Pressure Evaluation School
49
OVERBURDEN
PRESSURE
Formation Pressure
04/08/23 Formation Pressure Evaluation School
50
Overburden Pressure
• Overburden pressure is the pressure at any point in the formation exerted by the total weight of the overlying sediments.
• It is a function of the vertical depth and density of the rock column.
• The prior calculation of overburden pressure is critical for the accurate determination of pore and fracture pressures.
Formation Pressure
04/08/23 Formation Pressure Evaluation School
51
• Overburden calculation needs the following data to be input
– fluid density (offshore)
Measurefluid densityoffshore
Overburden Pressure
Formation Pressure
04/08/23 Formation Pressure Evaluation School
52
• Overburden calculation needs the following data to be input
– fluid density (offshore)– formation bulk density
Measure bulk densityof formations
Overburden Pressure
Formation Pressure
04/08/23 Formation Pressure Evaluation School
53
Measure vertical depth to point ofinterest.
• Overburden pressure needs the following data to be input
– fluid density (offshore)– formation bulk density– true vertical depth
Overburden Pressure
Formation Pressure
04/08/23 Formation Pressure Evaluation School
54
TVD
• Overburden pressure needs the following data to be input
– fluid density (offshore)– formation bulk density– true vertical depth
• Onshore, overburden pressure is calculated from ground level.
Overburden Pressure
Formation Pressure
04/08/23 Formation Pressure Evaluation School
55
TVD
• Overburden pressure needs the following data to be input
– fluid density (offshore)– formation bulk density– true vertical depth
• Onshore, overburden pressure is calculated from ground level.
• Offshore, overburden pressure is calculated from sea level.
• Overburden gradient is calculated from the drill floor.
Overburden Pressure
Formation Pressure
04/08/23 Formation Pressure Evaluation School
56
• Overburden is variable.
• Sediment densities vary between 1.6 and 3.2 gm/cc
• Fluid densities vary between 1.0 and 1.08 gm/cc
• Overburden pressure is calculated with :
S(psi) = pb(ppg) * tvd(ft) * 0.0519
S(bar) = pb(sg) * tvd(m) * 0.0981Where :
S = Overburden pressure (psi or bars)pb = bulk density (gm/cc or s.g. or ppg)tvd = interval depth or length (ft or m)
NOTE: The equation in the manual : S(psi) = tvd(ft) x density s.g. x 0.433 is best not used due to inaccuracies in wells shallower than 6000m.
Overburden Pressure
Formation Pressure
04/08/23 Formation Pressure Evaluation School
57
• At 60ft = 0 psi
• At 360 ft, – (300 * 8.67 * 0.0519) + 0– 135.0 psi– 135.0 / 360 = 0.375 psi/ft– 0.375 / 0.052 = 7.21 ppg
• At 700 ft, – (340 * 15.4 * 0.0519) + 135.0– 407.0 psi– 407.0 / 700 = 0.581 psi/ft– 0.581 / 0.052 = 11.18 ppg
• At 1500 ft, – (800 * 16.9 * 0.0519) + 407.0– 1108.0 psi– 1108.0 / 1500 = 0.739 psi/ft– 0.739 / 0.052 = 14.21 ppg
air
water
clay
shale
sandstone
limestone
0
15.4
20.3
16.9
20.9
8.6760ft
360ft
700ft
1500ft
2200ft
2500ft
OBG Calculation
Formation Pressure
04/08/23 Formation Pressure Evaluation School
58
• The basic data needed is bulk density.• Sources of bulk density data include :
– Drilled cuttings – Density wireline and MWD logs – Sonic wireline and MWD logs– Regional tables and curves – Equations– Seismic velocity data
Overburden Pressure Data
Formation Pressure
04/08/23 Formation Pressure Evaluation School
59
Using a Mud Balance
(Pyncometer Method)
• Grab some fresh cuttings• Remove obvious cavings• Clean off mud• Dry slightly on paper towel• Be consistent
• Put cuttings in the balance until it reads 8.34 ppg.• Fill the cup with fresh water and weigh again = (W2)• Calculate bulk density : pb (gm/cc) = 8.34 / (16.68 - W2)
OBG Data - Drilled Cuttings
Formation Pressure
04/08/23 Formation Pressure Evaluation School
60
• MWD and wireline density logs contain bulk density data that can be read directly from the log.
• Density logs only have a small depth of investigation (2-6 inches)
• Caution has to be taken when reading the logs due to washouts in the hole, mixed lithologies, logging speed etc.
• Logging companies will apply correction factors for the above.
• Allowance needs to be made for the effects that can distort density data such as gas filled pores - density reduction.
• Density log data is superior to density from drilled cuttings data or sonic log data but unfortunately it is not commonly run in all hole sections.
OBG Data - Density Logs
Formation Pressure
04/08/23 Formation Pressure Evaluation School
61
• Sonic logs register the Transit Time (delta t) of a formation. • Delta t is measured in usecs/ft.• The delta t for a particular rock is a measure of its porosity• Lower transit times = faster acoustic velocity
= lower porosity = higher density
• With depth and normal compaction density should increase.
LOWHIGH
Normal Trendfor Sonic (dt)with normalcompaction.
OBG Data - Sonic Logs
Formation Pressure
04/08/23 Formation Pressure Evaluation School
62
The procedure
• Using Gamma Ray or SP, pick broad lithology intervals• Ignore beds less than 50ft thick• Eyeball an average delta t over the lithology interval
or ...• Calculate the average delta t using Integrated Transit Time tics
• Each tic = 1000 usecs/ft• Count the tics over the interval -
use 1/2’s, 1/4’s if necessary• Calculate delta t :
delta t = #tics * 1000 / interval
OBG Data - Sonic Logs
Formation Pressure
04/08/23 Formation Pressure Evaluation School
63
• AGIP’s Bellotti, DiLorenza and Giacca (1978) developed an equation to calculate bulk density from Sonic logs :
pb = 2.75 - [(2.11 * (Dt - Dt Matrix) / (Dt + Dt Fluid)]
Where :
pb = bulk density
Dt = transit time from log
DtMatrix = transit time of rock
DtFluid = transit time of fluid
OBG Data - Sonic Logs
Formation Pressure
04/08/23 Formation Pressure Evaluation School
64
• Gardener’s Sonic Equation (used in Predict) was also developed to calculate bulk density from Sonic logs :
pb = A * ( 10^6 / Dt )^B
Where :
pb = bulk density
Dt = transit time from log
A = Coefficient (typically 0.23)
B = Exponent (typically 0.25)
OBG Data - Sonic Logs
Formation Pressure
04/08/23 Formation Pressure Evaluation School
65
• Seismic data can be used to calculate bulk density.
• Seismic velocity can be converted to usec/ft and treated as you would Sonic data:
Transit Time (usec/ft) = (1/vint) * 1,000,000
• Data taken around salt domes will not be reliable due to the effect salt has on sound waves - lowers the values.
• Try to get a "shallow" seismic study to check for existing faults.
• Even from the sparsest of data the pressure engineer should be able to produce a fairly reasonable overburden curve prior to drilling. Other data obtained during the drilling phase should be used to compare and correct this initial curve.
OBG Data - Seismic Data
Formation Pressure
04/08/23 Formation Pressure Evaluation School
66
• Seismic data may look something like this:
subsea depth two-way time velocity interval
6618 2.2672 82726668 2.2846 56846718 2.3008 62176768 2.3152 69096818 2.3292 71576868 2.3452 6242
Transit Time (usec/ft) = (1/vint) * 1,000,000
139.72 (usec/ft) = (1/7157) * 1,000,000
OBG Data - Seismic Data
Formation Pressure
04/08/23 Formation Pressure Evaluation School
67
• Many areas have regional curves based on known data.
• Problems arise when data is used outside the specific region.• Even within the area water depth corrections must be made.
• Remember to always question offset data and make sure it is not TOO offset by structure or distance.
• Make corrections for water depth. This can make a vast difference in overburden.
OBG Data - Curves and Tables
Formation Pressure
04/08/23 Formation Pressure Evaluation School
68
• Bryant (1989) came up with the following equation to calculate the overburden gradient for Tertiary basins :
OBG = OGO+2.64E-5(D)-1.97E-9(D^2)+6.60E-14(D^3)-5.97E-19(D^4)
Where:OGO = Overburden gradient offset -
(Land=0.87; Shallow=0.85; Deep=0.82)D = True vertical depth (ft)
• Another equation comes from Amoco/Chevron
• This equation approximates sediment bulk density (OBG will have to be calculated from these densities) :
pb = 16.3 + [ (TVD - Water Depth - Air Gap) / 3125 ] ^0.6
(Note : 16.3 is the estimated weight of sediments at the mudline)
OBG Data - Equations
Formation Pressure
04/08/23 Formation Pressure Evaluation School
69
• The generation of an overburden curve cannot be ignored.
• This is the curve that all other pressure work depends on.
• You should not wait until the first casing point.
With the reasonable offset data, an overburden curve can be made even before a foot of formation is drilled.
This can then be corrected as drilling progresses and more data is acquired.
Steps to creating your curve:
1) Use equations or data provided2) Use cuttings data to modify3) Use e-log data at casing points4) Continue to use cuttings, sonic, and density data, etc.5) Check curve with LOT’s
Overburden Pressure - Conclusion
Formation Pressure
04/08/23 Formation Pressure Evaluation School
70
Formation Pressure
Formation Pressure Worksheet Overburden Pressure Calculations
Air Gap 95.1 feet 29.0 metres OB Offsets: Sand dt 50 The OBG from Amoco uses the bulk
Water Depth 728.4 feet 222.0 metres Land 0.900 Silt dt 48 density equation w hich is used in
Normal PP 8.7 ppg 1.04 sg Shelf 0.825 Shale dt 47 "Predict" . The Bell equation needs
Deep 0.850 Sea dt 190 to use an OB Offset based on w ater
Fresh dt 210 depth. These are estimates only!
TVD (ft) TVD (m) pB Amoco pB Cutting dt Sonic dt Matrix pB Sonic pB Used OBP (psi) OBP (bar) OBG (ppg) OBG (sg) (ppg) (sg) (ppg) (sg)
984.3 300.0 1.97 1.97 466.3 32.1 9.1 1.09 9.1 1.09 9.1 1.081148.3 350.0 1.98 1.98 607.2 41.9 10.2 1.22 10.2 1.22 10.1 1.211312.3 400.0 1.99 1.99 748.8 51.6 11.0 1.32 11.0 1.32 10.9 1.301476.4 450.0 2.00 2.00 890.9 61.4 11.6 1.39 11.6 1.39 11.5 1.381640.4 500.0 2.01 2.01 1033.5 71.3 12.1 1.45 12.1 1.45 12.1 1.451804.5 550.0 2.01 2.01 1176.5 81.1 12.6 1.51 12.6 1.51 12.6 1.501968.5 600.0 2.02 1.85 2.02 1319.9 91.0 12.9 1.55 12.9 1.55 13.0 1.552132.5 650.0 2.02 2.00 2.02 1463.8 100.9 13.2 1.58 13.2 1.58 13.3 1.602296.6 700.0 2.03 1.90 2.03 1608.0 110.9 13.5 1.62 13.5 1.62 13.7 1.642460.6 750.0 2.03 1.90 2.03 1752.5 120.8 13.7 1.64 13.7 1.64 14.0 1.672624.7 800.0 2.04 1.90 2.04 1897.4 130.8 13.9 1.67 13.9 1.67 14.2 1.712788.7 850.0 2.04 1.88 2.04 2042.6 140.8 14.1 1.69 14.1 1.69 14.5 1.742952.7 900.0 2.05 2.05 2188.2 150.9 14.3 1.71 14.3 1.71 14.7 1.763116.8 950.0 2.05 2.05 2334.0 160.9 14.4 1.73 14.4 1.73 14.9 1.793280.8 1000.0 2.06 1.95 2.06 2480.1 171.0 14.6 1.75 14.6 1.75 15.1 1.813444.9 1050.0 2.06 1.90 2.06 2626.6 181.1 14.7 1.76 14.7 1.76 15.3 1.843608.9 1100.0 2.07 2.07 2773.3 191.2 14.8 1.77 14.8 1.77 15.5 1.863772.9 1150.0 2.07 2.07 2920.3 201.3 14.9 1.79 14.9 1.79 15.7 1.883937.0 1200.0 2.07 2.07 3067.6 211.5 15.0 1.80 15.0 1.80 15.9 1.904101.0 1250.0 2.08 2.08 3215.1 221.7 15.1 1.81 15.1 1.81 16.0 1.924265.1 1300.0 2.08 2.08 3362.9 231.9 15.2 1.82 15.2 1.82 16.2 1.944429.1 1350.0 2.08 2.08 3510.9 242.1 15.3 1.83 15.3 1.83 16.3 1.964593.1 1400.0 2.09 2.10 150.0 48 2.12 2.10 3660.1 252.4 15.4 1.84 15.4 1.84 16.5 1.97
OBG Amoco OBG Bell
Well - Bideford - 31/7 : Grossenschmuck : Celtic Petroleum
OBG Used For Analysis
04/08/23 Formation Pressure Evaluation School
71
Formation Pressure
0.0100.0200.0300.0400.0500.0600.0700.0800.0900.0
1000.01100.01200.01300.01400.01500.01600.01700.01800.01900.02000.02100.02200.02300.02400.02500.02600.02700.02800.02900.03000.03100.03200.03300.03400.0
0.50 0.70 0.90 1.10 1.30 1.50 1.70 1.90 2.10 2.30 2.50
obg s.g.
dep
th m
.
OBG Used For Analysis
OBG Amoco
OBG Bell
04/08/23 Formation Pressure Evaluation School
72
Formation Pressure
• Use the Bideford 31/7 well logs.
• Select Sonic transit time data points every 100 meters.
• Calculate the bulk density using Gardener’s equation.
• Calculate the overburden gradient in EMW.
• Use 1.03 s.g. as the water density.
• Use the Amoco equation to calculate bulk density values every 100 meters from the seafloor to the top of the first sonic data point.
Day One : Homework : OBG