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Preface
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Introduction to Energy Geomechanics
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Introduction to Energy Geomechanics
Contents
1
. Introduction
1
.
1
Structural Geology
1
.
2
Geomechanics in the Energy Industry
1
.
2
.
1
Drilling and Wellbore Stability
1
.
2
.
2
Wellbore Completion
1
.
2
.
3
Reservoir Geomechanics
1
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2
.
4
Carbon and Hydrogen Geological Storage
1
.
2
.
5
Geothermal Energy
1
.
3
Problems
1
.
4
Further Reading and References
2
. Subsurface Stresses and Pore Pressure
2
.
1
Lithostatic gradient
2
.
1
.
1
Stress concept and equilibrium 1D
2
.
1
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2
Rock vertical stress gradient
2
.
2
Non-hydrostatic pore pressure
2
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2
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1
Mechanisms of overpressure
2
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2
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2
Disequilibrium compaction and excess pore pressure
2
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2
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3
Reservoir depletion
2
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3
Horizontal stresses
2
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3
.
1
Background
2
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3
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2
Geological indicators
2
.
3
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3
In-situ measurement
2
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3
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4
Stress Regimes
2
.
3
.
5
Ideal orientation of open-mode fractures
2
.
4
Problems
2
.
5
Coding support for solving problems
2
.
6
Further reading and references
3
. Fundamentals of Solid Continuum Mechanics
3
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1
Stress tensor
3
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1
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1
Cauchy's equations of stress equilibrium
3
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1
.
2
Application of Cauchy's equations for total vertical stress calculation
3
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1
.
3
Continuum mechanics solution of an arbitrary problem
3
.
2
Kinematic equations: displacements and strains
3
.
3
Constitutive equation: stress-strain relationships
3
.
3
.
1
Linear isotropic elasticity
3
.
3
.
2
The isotropic solid in Voigt notation
3
.
3
.
3
Effective stress and elasticity
3
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3
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4
Calculation of horizontal stress according to linear elasticity
3
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3
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5
Calculation of reservoir compressibility with linear elasticity
3
.
3
.
6
Generalized linear elasticity problem
3
.
4
Elastic anisotropy
3
.
5
Permanent deformation: Elasto-plasticity
3
.
6
Time-dependent deformation: Visco-elasticity
3
.
7
Multiphysics problems
3
.
7
.
1
Poro-elasticity
3
.
7
.
2
Thermo-elasticity
3
.
8
Problems
3
.
9
Coding support for solving problems
3
.
10
Further reading and references
4
. Rock Yield and Failure
4
.
1
Preliminary concepts
4
.
1
.
1
Microstructure of geologic materials
4
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1
.
2
Length scales v.s. process zone size
4
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1
.
3
Overview of types of rock failure
4
.
2
Tensile failure
4
.
2
.
1
Direct tension
4
.
2
.
2
The Brazilian test
4
.
3
Shear failure
4
.
3
.
1
Frictional Strength
4
.
3
.
2
Unconfined compression strength
4
.
3
.
3
Confined strength: the triaxial test
4
.
3
.
4
Triaxial tests of fluid saturated rocks and sediments
4
.
4
Compression failure: Pore collapse
4
.
5
Yield/failure locus
4
.
6
Strength anisotropy
4
.
7
Deformation beyond the elastic limit
4
.
8
Rock damage and failure revisited
4
.
9
Problems
4
.
10
Further reading and references
5
. Stresses on Faults and Fractures
5
.
1
Introduction
5
.
2
Mapping of faults and fractures
5
.
2
.
1
Orientation of planes with respect to the geographical coordinate system
5
.
2
.
2
Stereonets for plotting fault orientation
5
.
2
.
3
Faults in geological maps
5
.
3
Frictional strength of faults and fault types
5
.
3
.
1
Fault strength
5
.
3
.
2
Normal faults
5
.
3
.
3
Thrust and reverse faults
5
.
3
.
4
Strike-slip faults
5
.
3
.
5
Stress and faulting regimes
5
.
3
.
6
Ideal orientation of faults
5
.
4
Determination of normal and shear stresses on the fault plane
5
.
4
.
1
Mohr's circle method
5
.
4
.
2
Tensor method
5
.
5
Applications
5
.
5
.
1
Critically stressed fractures and permeability
5
.
5
.
2
Determination of horizontal stresses assuming limit equilibrium
5
.
5
.
3
Determination of stress regime and horizontal stress direction from fault orientation
5
.
5
.
4
Fault reactivation
5
.
6
Problems
5
.
7
Further reading and references
6
. Wellbore Stability
6
.
1
The wellbore environment
6
.
2
Kirsch solution for stresses around a cylindrical cavity
6
.
2
.
1
Cylindrical coordinate system
6
.
2
.
2
Kirsch solution components
6
.
2
.
3
Complete Kirsch solution
6
.
3
Shear failure and wellbore breakouts
6
.
3
.
1
Breakout angle determination
6
.
3
.
2
Breakout measurement
6
.
3
.
3
Maximum horizontal stress determination from breakout angle
6
.
4
Tensile fractures and wellbore breakdown
6
.
4
.
1
Identification of tensile fractures in wellbores
6
.
5
The mud window
6
.
6
Mechanical stability of deviated wellbores
6
.
6
.
1
Wellbore orientation
6
.
6
.
2
Calculation of stresses on deviated wellbores
6
.
6
.
3
Breakout analysis for deviated wellbores
6
.
6
.
4
Tensile fractures analysis for deviated wellbores
6
.
7
Thermal, chemical, and leak-off effects on wellbore stability
6
.
7
.
1
Thermal effects
6
.
7
.
2
Chemo-electrical effects
6
.
7
.
3
Leak-off effects
6
.
8
Strength anisotropy
6
.
9
Problems
6
.
10
Further reading and references
7
. Hydraulic fracturing
7
.
1
Fluid-driven fractures in nature
7
.
2
Hydraulic fracture injection/shut-in tests
7
.
2
.
1
Leak-off test
7
.
2
.
2
Diagnostic fracture initiation test (DFIT)
7
.
2
.
3
Step-rate test
7
.
3
Hydraulic fracture design: Single fracture completion
7
.
3
.
1
Improvement of reservoir access and wellbore-reservoir surface area
7
.
3
.
2
The coupled fluid-driven fracture propagation problem
7
.
3
.
3
Fracture design: Single planar models
7
.
3
.
4
Stress logs and implications on hydraulic fracture height
7
.
4
Multistage hydraulic fracturing
7
.
4
.
1
Increased surface area with multiple fractures
7
.
4
.
2
Fracture interference and fracture hit
7
.
4
.
3
Fracture reactivation, microseismicity, and optical fiber monitoring
7
.
4
.
4
Multiple strands in hydraulic fracture propagation
7
.
5
Practical aspects of hydraulic fracturing
7
.
6
Problems
7
.
7
Suggested Reading
8
. Reservoir depletion and injection
8
.
1
Changes of stress in the reservoir rock
8
.
1
.
1
Rock compressibility and permeability
8
.
1
.
2
Linear poroelasticity solution
8
.
2
Changes of stress in the vicinity of the reservoir
8
.
3
Fluid injection
8
.
4
Fault stability
8
.
5
Suggested Reading
