Taiwan Chelungpu Drilling Project Taiwan Chelungpu-Fault Drilling Project Meeting Mark Zoback Stanford University October 21, 2003 In Situ Stress Measurements, Wellbore Stability and Fault Mechanics

Taiwan Chelungpu Drilling Project Obtaining a Comprehensive Geomechanical Model Vertical stress S v z 0   g dz 0 z 0  S hmin  LOT, XLOT, minifrac Least principal stress S Hmax magnitude  modeling wellbore failures Max. Horizontal Stress Pore pressure P p  Measure, sonic, seismic StressOrientation Orientation of Wellbore failures ParameterData Rock Strength Logs, Modeling Wellbore failure, Lab Faults/Bedding Planes Wellbore Imaging

Taiwan Chelungpu Drilling Project Will There be Problems Drilling through Dipping Shales? (Shale Reaction with Mud/Stress State and Weak Bedding Planes)

Taiwan Chelungpu Drilling Project What is the stress state before/after Chi Chi Earthquake?

Taiwan Chelungpu Drilling Project What can we learn from the stress state after the earthquake? Kaj Johnson

Taiwan Chelungpu Drilling Project Obtaining a Comprehensive Geomechanical Model Vertical stress S v z 0   g dz 0 z 0  S hmin  LOT, XLOT, minifrac Least principal stress S Hmax magnitude  modeling wellbore failures Max. Horizontal Stress Pore pressure P p  Measure, sonic, seismic Stress Orientation Orientation of Wellbore failures ParameterData Rock Strength Logs, Modeling Wellbore failure, Lab Faults/Bedding Planes Wellbore Imaging

Taiwan Chelungpu Drilling Project Hydraulic Fractures Propagate Perpendicular to the Least Principal Stress

Taiwan Chelungpu Drilling Project Extended Leak-Off Test

Taiwan Chelungpu Drilling Project Visund Field

Taiwan Chelungpu Drilling Project Obtaining a Comprehensive Geomechanical Model Vertical stress S v z 0   g dz 0 z 0  S hmin  LOT, XLOT, minifrac Least principal stress S Hmax magnitude  modeling wellbore failures Max. Horizontal Stress Pore pressure P p  Measure, sonic, seismic Stress Orientation Orientation of Wellbore failures ParameterData Rock Strength Logs, Modeling Wellbore failure, Lab Faults/Bedding Planes Wellbore Imaging

Taiwan Chelungpu Drilling Project Stress Concentration Around a Vertical Well

Taiwan Chelungpu Drilling Project Stress-Induced Wellbore Failures UBI Well AFMI Well B

Taiwan Chelungpu Drilling Project Stress Orientations in North America

Taiwan Chelungpu Drilling Project

Taiwan Chelungpu Drilling Project Drilling Induced Tensile Wall Fractures FMI FMS

Taiwan Chelungpu Drilling Project Visund Stress Field Orientations

Taiwan Chelungpu Drilling Project Obtaining a Comprehensive Geomechanical Model Vertical stress S v z 0   g dz 0 z 0  S hmin  LOT, XLOT, minifrac Least principal stress S Hmax magnitude  modeling wellbore failures Max. Horizontal Stress Pore pressure P p  Measure, sonic, seismic Stress Orientation Orientation of Wellbore failures ParameterData Rock Strength Logs, Modeling Wellbore failure, Lab Faults/Bedding Planes Wellbore Imaging

Taiwan Chelungpu Drilling Project Eq. No.UCS, MPaRegion Where DevelopedGeneral CommentsReference (304.8/  t) 2.93 North SeaMostly high porosity Tertiary shalesHorsrud (2001) (304.8/  t) 3.2 Gulf of MexicoPliocene and youngerUnpublished (304.8/  t) 2.6 Globally-Unpublished (304.8/  t) 3 Gulf of Mexico-Unpublished (304.8/  t –1) North Sea -Lal (1999) E Strong and compacted shalesUnpublished  Low porosity (  < 0.1) shales Lashkaripour and Dusseault (1993)  –0.96 North SeaMostly high porosity Tertiary shalesHorsrud (2001)  High porosity (  > 0.27) shales Unpublished UCS Models for Shale

Taiwan Chelungpu Drilling Project Horsrud (  ) - # Unconfined Compressive Strength Coefficient of internal friction psi

Taiwan Chelungpu Drilling Project Obtaining a Comprehensive Geomechanical Model Vertical stress S v z 0   g dz 0 z 0  S hmin  LOT, XLOT, minifrac Least principal stress S Hmax magnitude  modeling wellbore failures Max. Horizontal Stress Pore pressure P p  Measure, sonic, seismic Stress Orientation Orientation of Wellbore failures ParameterData Rock Strength Logs, Modeling Wellbore failure, Lab Faults/Bedding Planes Wellbore Imaging

Taiwan Chelungpu Drilling Project UBI FMI Image Logs from the SAFOD Pilot Hole

Taiwan Chelungpu Drilling Project Obtaining a Comprehensive Geomechanical Model Vertical stress S v z 0   g dz 0 z 0  S hmin  LOT, XLOT, minifrac Least principal stress S Hmax magnitude  modeling wellbore failures Max. Horizontal Stress Pore pressure P p  Measure, sonic, seismic Stress Orientation Orientation of Wellbore failures ParameterData Rock Strength Logs, Modeling Wellbore failure, Lab Faults/Bedding Planes Wellbore Imaging

Taiwan Chelungpu Drilling Project KTB Stress Profile Zoback and Harjes (1997)

Taiwan Chelungpu Drilling Project Visund Magnitudes - Strike-Slip (Almost Reverse)

Taiwan Chelungpu Drilling Project Well-54 (FMS) Well-30 (HDT) Well-27 (HDT) Reverse/Strike Slip S Hmax >>S hmin ~S v Central Australia

Taiwan Chelungpu Drilling Project Will There be Problems Drilling through Dipping Shales? (Shale Reaction with Mud/Stress State and Weak Bedding Planes)

Taiwan Chelungpu Drilling Project Stable Wellbores Depend on Controlling the Width of Breakouts

Taiwan Chelungpu Drilling Project Well design usually means mud window and casing

Taiwan Chelungpu Drilling Project Weak bedding introduces strength anisotropy if Rock mechanics test on rocks with weak planes

Taiwan Chelungpu Drilling Project Weak Bedding Planes Can be a Source of Wellbore Instability

Taiwan Chelungpu Drilling Project Weak Bedding Planes Causing Enlarged Breakouts in Shale

Taiwan Chelungpu Drilling Project

Taiwan Chelungpu Drilling Project PG-2 abandoned Side Track GIG-3 Successful Result Result Company successfully drilled well GIG-3 through the FB Shale by limiting deviation to 27° and mud weights to 10.5 ppg – 11 ppg Company avoided costly stability problems by following GMI’s recommendations for this well

Taiwan Chelungpu Drilling Project Modeling anisotropic breakouts in the FB shale with the given in situ stress state Anisotropic failure MW = 10.5 ppg Isotropic failure Anisotropic failure MW = 12 ppg Observed Bedding plane properties: dip = 8° (from core data) Azi = 23° (from core data) S 0 = 4.8 MPa (from lab data)  s = 0.21 (from lab data) Result: The in situ stress tensor derived in this study and the bedding plane properties measured in the lab can account for the anisotropic breakouts seen in the FB shale

Taiwan Chelungpu Drilling Project What is the stress state before/after Chi Chi Earthquake?

Taiwan Chelungpu Drilling Project Can We Use Wellbore Observations to Identify Presence of Active Faults? Anomalous stress orientations Anomalous stress magnitudes Anomalous stress orientations Anomalous stress magnitudes

Taiwan Chelungpu Drilling Project Drilling-Induced Slip and Breakout Perturbation

Taiwan Chelungpu Drilling Project Anomalous Breakout Orientations

Taiwan Chelungpu Drilling Project Wellbore Breakout Rotations Due to Fault Slip

Taiwan Chelungpu Drilling Project Drilling-Induced Tensile Fractures Rotated Near Fault at 3100 meters

Taiwan Chelungpu Drilling Project Modeling Fault-Induced Stress Perturbations at the Wellbore Wall

Taiwan Chelungpu Drilling Project KTB Stress Orientation Profile

Taiwan Chelungpu Drilling Project Johnson and Segall (in press) Co-Seismic Slip Model of Chi-Chi Earthquake (GPS)

Taiwan Chelungpu Drilling Project What can we learn from measuring the stress state after the earthquake? Kaj Johnson

Taiwan Chelungpu Drilling Project SummarySummary Obtaining a Comprehensive Geomechanical Model can provide insight and help in addressing wellbore stability problems as drilling is underway and can make important contributions to the fundamental scientific objectives of the project Engineering – Must build the model as you go – “real time” analysis with careful mud logging (cuttings analysis) Science – Obtain critical data as project is being carried out - can’t go back and get missing data Obtaining a Comprehensive Geomechanical Model can provide insight and help in addressing wellbore stability problems as drilling is underway and can make important contributions to the fundamental scientific objectives of the project Engineering – Must build the model as you go – “real time” analysis with careful mud logging (cuttings analysis) Science – Obtain critical data as project is being carried out - can’t go back and get missing data

Taiwan Chelungpu Drilling Project RecommendationsRecommendations Obtain logs after each phase of drillingObtain logs after each phase of drilling –A complete suite of geophysical logs –Wellbore image logs are essential (both ultrasonic and electrical, if possible) Carry out an Extended Leak Off Test (hydrofrac) each time casing is setCarry out an Extended Leak Off Test (hydrofrac) each time casing is set Carry out additional hydrofracs (if possible) – only to measure S 3Carry out additional hydrofracs (if possible) – only to measure S 3 Carry out careful mud logging as drilling is underway. Laboratory tests on core samples will be important primarily for scienceCarry out careful mud logging as drilling is underway. Laboratory tests on core samples will be important primarily for science Make data available to science team as rapidly as possibleMake data available to science team as rapidly as possible Obtain logs after each phase of drillingObtain logs after each phase of drilling –A complete suite of geophysical logs –Wellbore image logs are essential (both ultrasonic and electrical, if possible) Carry out an Extended Leak Off Test (hydrofrac) each time casing is setCarry out an Extended Leak Off Test (hydrofrac) each time casing is set Carry out additional hydrofracs (if possible) – only to measure S 3Carry out additional hydrofracs (if possible) – only to measure S 3 Carry out careful mud logging as drilling is underway. Laboratory tests on core samples will be important primarily for scienceCarry out careful mud logging as drilling is underway. Laboratory tests on core samples will be important primarily for science Make data available to science team as rapidly as possibleMake data available to science team as rapidly as possible

Taiwan Chelungpu Drilling Project Most Importantly GOOD LUCK To us all! GOOD LUCK To us all!