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Divine Somiari,S Well Bore Stability Presentation
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Transcript of Divine Somiari,S Well Bore Stability Presentation
WELLBORE STABILITY
JUMA . E. OIL & GAS SERVICES
TRADITIONAL WELL DESIGN
Traditional well design is based on pore and fracture pressure
estimate from offset wells and log-based analysis
This method is typically less reliable when drilling • Deviated wells• In tectonic areas• Dipping weak bedded formations • In depleted reservoir
And costs the industry a lot of money, approximately $8.00 billion yearly.
Case Study, Niger Delta, NigeriaComparison Between Traditional & Geo-
mechanics method of Well Planning • Below is a table (table 6) showing mud
weight values estimated for a well using traditional method. While drilling with the estimated mud weight value of 0.53 to 0.57psi/ft, by the traditional method, it was not possible to drill to TD.
• With geo-mechanics used, a mud weight of 0.36 psi/ft was estimated (table 2). These mud weight was able to drill a sidetrack of the well to TD, with out any non productive loss time due to well bore instability problems.
TABLE 1
Fracture Gradient (psi/ft) Mud Weight (psi/ft) Mud Overbalance (psi/ft)
0.603133333333333 0.526666666666667 0.0764666666666666
0.6048 0.536956307031351 0.0867563070313506
0.6068 0.5285 0.0783
0.608133333333333 0.529166666666667 0.0789666666666667
0.609133333333333 0.529666666666667 0.0794666666666666
0.610133333333333 0.530166666666667 0.0799666666666667
0.6118 0.531 0.0808
0.642906666666667 0.566633333333333 0.0762733333333333
0.64424 0.5673 0.0769399999999999
0.644906666666667 0.567633333333333 0.0772733333333333
0.646906666666667 0.568633333333333 0.0782733333333333
0.64724 0.5688 0.07844
HOW CAN WELLBORE STABILITY ADD VALUE TO THE INDUSTRY?
By reducing expensive drilling problems • Well bore instability and fracture pressure prediction • Reduce stuck pipe, losses, side tracks, reaming, etc• Under balanced drilling, feasibility.
By increasing reservoir performance.• Production from natural fractures • Sand production prediction. • Reduce casing shear and collapse • Compaction / subsidence
By reducing exploration risk• Fault leakage analysis
THE GEOMECHANICAL MODEL
This based on the principal stress tensor
Description of a geo mechanical model for a reservoir
involves detailed knowledge of:• In situ stress orientations• In situ stress magnitudes • Pore pressure • Rock Mechanical properties
Other consideration: Mud chemistry, weak bedding planes,
Fractures, thermal effects.
BUILDING A GEOMECHANICAL MODEL
Data required to construct a geo mechanical model:
• Vertical or overburden stress from integrated density log• Pore pressure from log-based (sonic, resistively)• Seismic (ITT, Velocity cubes) and Measurement (RFT,
PWD, etc)• Magnitude of Minimum horizontal stress from LOT,
XLOT, etc)• Rock Strength from Logs, core test, etc
PORE PRESSURE, FRACTURE, PRESSURE, AND WELL BORE STABILITY
THE COMPLETE PICTURE
Well planning and drilling should incorporate:
Geomechanics to reduce wellbore instability and lost circulation risk.
This is especially important for high angle wells, tectonic areas and
depleted reservoirs.
Pore pressure and well bore stability prediction should be performed
Together as these will give clearer picture of the formation.
WELL BORE STABILITY
Aim:
Reduce drilling costs by incorporating Geomechanics into well
planning and drilling process:• Optimizing mud weights and mud properties • Minimizing casing strings • Optimizing wellbore trajectory • Optimizing surface location
Case Study, Niger Delta, Nigeria.
• Wellbore Stability Analysis Plots to illustrate the use of geo-mechnics to add value to the planning and drilling of a well in Niger Delta.
TABLE 2
Depth (ft)Overburden Stress (psi/ft)
Pore Pressure (psi/ft)
8240 0.909 0.45
8710 0.914 0.45
9283 0.92 0.45
9753 0.924 0.45
10043 0.927 0.45
10347 0.93 0.45
10917 0.935 0.45
12584 0.948 0.45
13204 0.952 0.45
13614 0.954 0.45
14368 0.96 0.45
14498 0.961 0.45
TABLE 3Minimum Horizontal Stress (psi/ft)
Well Inclination(deg)
Well azimuth(deg)
0.469666667 0 0
0.471333333 5 5
0.473333333 10 10
0.474666667 15 15
0.475666667 20 20
0.476666667 25 25
0.478333333 30 30
0.482666667 35 35
0.484 40 40
0.484666667 45 45
0.486666667 50 50
0.487 55 55
TABLE 4
Poisson's Ratio Friction angle(deg) UCS (psi/ft)
0.25 25.4 0.289
0.25 26.7 0.3596
0.25 24.9 0.2243
0.25 25.4 0.2393
0.25 25.4 0.2324
0.25 25.4 0.233
0.25 26.2 0.2633
0.25 26.7 0.2487
0.25 28 0.294
0.25 27.2 0.2518
0.25 29.7 0.3291
0.25 29.7 0.3261
TABLE 5
Compressional Velocity Shear Velocity Maximum Horizontal Stress (psi/ft)
45 5 0.667366666666667
56 10 0.670533333333333
67 15 0.674333333333333
78 20 0.676866666666667
89 25 0.678766666666667
100 30 0.680666666666667
111 35 0.683833333333333
122 40 0.692066666666667
133 45 0.6946
144 50 0.695866666666667
155 55 0.699666666666667
166 60 0.7003
TABLE 6
Collapse Pressure (psi/ft) Fracture Gradient (psi/ft) Mud Weight (psi/ft)
0.479896447759961 0.469666666666667 0.474781557213314
0.56093485246493 0.471333333333333 0.516134092899132
0.417355126422702 0.473333333333333 0.445344229878018
0.440704205542267 0.474666666666667 0.457685436104467
0.439936355143774 0.475666666666667 0.45780151090522
0.447046417631349 0.476666666666667 0.461856542149008
0.489090182237921 0.478333333333333 0.483711757785627
0.483988464233271 0.482666666666667 0.483327565449969
0.53901938462006 0.484 0.51150969231003
0.487310584993971 0.484666666666667 0.485988625830319
0.575089388054011 0.486666666666667 0.530878027360339
0.560433280276301 0.487 0.523716640138151
TABLE 7
Mud Overbalance (psi/ft)
Distance from Fault (ft)
Open Hole Time (Second(s))
Deplected Pore Pressure
0.224781557213314
10000 0.234989743562158 0.25
0.266134092899132
10000 0.292395542508484 0.25
0.195344229878018
10000 0.182381313083017 0.25
0.207685436104467
10000 0.194578012575863 0.25
0.20780151090522 10000 0.188967530809154 0.250.211856542149008
10000 0.189455398788868 0.25
0.233711757785627
10000 0.214092731764416 0.25
0.233327565449969
10000 0.20222127759138 0.25
0.26150969231003 10000 0.239055310059773 0.250.235988625830319
10000 0.204741928819901 0.25
0.280878027360339
10000 0.267595586873032 0.25
0.273716640138151
10000 0.265156246974463 0.25