Reservoir Geomechanics Book

Preface xi

Part I Basic Principles

1 The tectonic stress field 3

Why stress is important 3

Stress in the earth's crust 4

Basic definitions 5

Relative stress magnitudes and E.M. Anderson's classification scheme 8

Stress magnitudes at depth 12

Measuring in situ stress 14

Indicators of contemporary stress orientation and relative magnitude 16

Regional stress patterns 18

Frictionless interfaces 24

2 Pore pressure at depth in sedimentary basins 27

Basic definitions 27

Reservoir compartmentalization 29

Mechanisms of overpressure generation 40

Estimating pore pressure at depth 44

3 Basic constitutive laws 56

Linear elasticity 61

Elastic moduli and seismic wave velocity 63

Elasticity anisotropy 65

Poroelasticity and effective stress 65

Poroelasticity and dispersion 69

Viscous deformation in uncemented sands 72

Thermoporoelasticity 83

4 Rock failure in compression, tension and shear 84

Rock strength in compression 87

Compressive strength criteria 92

Strength and pore pressure 104

Rock strength anisotropy 105

Estimating rock strength from geophysical log data 107

Shear-enhanced compaction 118

Tensile rock failure 121

Shear failure and the frictional strength of rocks 123

The critically stressed crust 127

Limits on in situ stress from the frictional strength of faults 130

Stress polygon 137

5 Faults and fractures at depth 140

Faults, fractures and fluid flow 142

Wellbore imaging 146

Representation of fracture and fault data at depth 149

Three-dimensional Mohr diagrams 154

Earthquake focal mechanisms 158

Part II Measuring Stress Orientation and Magnitude

6 Compressive and tensile failures in vertical wells167

Stress concentration around a cylindrical hole and wellbore failure 169

Quality ranking system for stress indicators 187

More on drilling-induced tensile fractures 190

More on wellbore breakouts 196

7 Determination of S3 from mini-fracs and extended leak-off tests and constraining the magnitude of SHmax from wellbore failure in vertical wells 206

Hydraulic fracturing to determine S3 208

Can hydraulic fracturing be used to estimate the magnitude of SHmax? 220

Wellbore failure and the determination of SHmax 222

Drilling-induced tensile fractures and the magnitude of SHmax 228

Estimating rock strength from breakouts when tensile fractures are present 231

Estimating SHmax from breakout rotations 231

Summary 233

8 Wellbore failure and stress determination in deviated wells 235

State of stress surrounding an arbitrarily deviated well 236

Failure of arbitrarily deviated wells 239

Confirming that SHmax and Shmin are principal stresses 246

Estimating SHmax from breakouts and tensile fractures in deviated wells 247

Distinguishing drilling-induced tensile fractures from natural fractures 252

Determination of SHmax orientation from shear velocity anisotropy in deviated wells 255

9 Stress fields - from tectonic plates to reservoirs around the world 266

Global stress patterns 266

Sources of crustal stress 270

Normal faulting stress fields in sedimentary basins 273

Methods for approximating Shmin in normal faulting areas 281

Compressional stress states in sedimentary basins 287

A few more comments about the bilateral constraint 292

Interpolation and extrapolation of stress magnitude data 294

Part III Applications

10 Wellbore stability 301

Preventing wellbore instability during drilling 303

Quantitative risk assessment 312

Role of rock strength anisotropy 317

Mud/rock interaction 321

Maximizing the frac gradient 322

Mud penetration and time-dependent wellbore failure 330

Preventing sand production 331

11 Critically stressed faults and fluid flow 340

Fractured reservoirs and permeability anisotropy 341

Some representative case studies 349

Identification of critically stressed faults and breakout rotations 358

Intentionally induced microseismicity to enhance permeability 360

Fault seal/blown trap 362

Dynamic constraints on hydrocarbon migration 369

12 Effects of reservoir depletion 378

Stress changes in depleting reservoirs 380

Deformation in depleting reservoirs 397

Deformation and stress changes outside of depleting reservoirs 412

References 423

Index 445