Seismic Geomechanics
How to Build and Calibrate Geomechanical Models using 3D and 4D Seismic Data (EET 5)
- By J. Herwanger and N. Koutsabeloulis
- Format: EPUB
- Publication Year: 2011
- Number of Pages: 181
- Language: English
- Ebook ISBN: 9789462820005
Three-dimensional geomechanical models have seen a rapid increase in use by the oil and gas industry, with applications from drilling to reservoir management. Yet few university programmes include applied geomechanics as part of their curriculum. This course aims to fill this gap and presents currently available methods to build, calibrate and interpret 3D and 4D geomechanical models. The course participant will become comfortable with stress and strain tensors, understand the basics of deriving elastic and strength properties, learn how to use seismic data to build geomechanical models and understand the importance of calibrating geomechanical models with observations.
Book DOI:
https://doi.org/10.3997/9789462820005
Table of Contents
Cover
Title Page
Copyright Page
Dedication
Acknowledgements
Contents
1 Introduction
1.1 Doctor, does my reservoir suffer from stress?
1.2 When does a rock break under stress?
1.3 Is my reservoir a lemon?
1.4 Common stress-related diseases in your reservoir
1.5 Is there anything positive about stress?
1.6 When to call the doctor?
1.7 Your guide to this lecture
2 Building a Reservoir Geomechanical Model
2.1 Introduction
2.2 3D mechanical earth models
2.3 4D mechanical earth models
2.3.1 Coupled reservoir and geomechanical modelling
2.4 Geometric description of model
2.5 Rock property determination
2.5.1 Rock properties for synthetic model
2.5.2 Static elastic properties
2.5.3 Dynamic-to-static elastic property correlations
2.5.4 Strength properties
Strength properties for shear failure
Strength properties for compaction failure
Strength properties for tensile failure
Composite failure surface
Fault properties
2.5.5 Strength property correlations
2.5.6 Property population in 3D
2.6 Boundary conditions
2.6.1 Displacement and stress boundary conditions
2.6.2 Equilibration and virtual stresses
2.6.3 Calibration with observed stress attributes
2.7 Well location and production rates
2.8 Discussion
3 Analysis of Production-Induced Deformation and Stress Changes
3.1 Introduction
3.2 Understanding and displaying tensors
3.2.1 Stress and strain
3.2.2 Engineering strain
3.3 Field-wide analysis of (vector) deformation and (tensor) stress changes
3.3.1 Deformation and stress changes in the near-surface section
3.3.2 Deformation and stress changes in the deep overburden and caprock
3.3.3 Deformation and stress changes in the reservoir
3.4 Stress arching
3.5 Reservoir compaction, overburden subsidence and underburden rebound
3.5.1 Influence of underburden stiffness
3.5.2 Influence of reservoir width and depth
3.6 Summary
4 Rock Physics for Geomechanics
4.1 Introduction
4.2 Describing anisotropic elastic wave velocity
4.3 Confining pressure, pore pressure, effective pressure and velocity
4.4 Observations of anisotropic velocity as a function of effective pressure
4.4.1 Laboratory measurements of elastic stiffness tensor
4.4.2 Stiffness tensor as a function of effective pressure
4.4.3 Velocity and velocity anisotropy as a function of effective pressure
4.5 Dependence of anisotropic velocity on triaxial stress state
4.5.1 Laboratory experiments
Hydrostatic compression test
Uniaxial strain test
Triaxial and polyaxial tests
4.5.2 Third-order elasticity theory
4.5.3 Deriving stress sensitivity parameters
Hydrostatic experiment in isotropic rock
Hydrostatic experiment in VTI anisotropic rock
Triaxial experiments
Limitations of third-order elasticity
4.6 Predictions of anisotropic velocity changes due to triaxial stress changes
4.6.1 Stiffness tensor and Thomsen parameters for hydrostatic compaction, uniaxial strain and deformation with zero volumetric strain
Example 1: Jurassic shale
Example 2: Colton sandstone
4.6.2 P-wave velocity in the caprock
4.6.3 S-wave velocity and polarization in the subsidence bowl
4.7 R-factor as a special case of triaxial stress changes
4.7.1 Deriving the R-factor model from third-order elasticity
4.7.2 Comparison of vertical velocity from third-order elasticity and R-factor model
4.7.3 R-factor prediction for hydrostatic compaction, uniaxial strain and deformation with zero volumetric strain
4.8 Discussion of stress sensitivity of velocities
4.8.1 Loading versus unloading
4.8.2 Velocity during simulated reservoir compaction
4.9 Summary
5 Geomechanical Effects in Time-Lapse Seismic Data
5.1 Introduction
5.2 Review of field examples
5.2.1 Observations of time-lapse timeshifts
5.2.2 Applications of overburden timeshift measurements
5.2.3 Recent advances in measurement and interpretation of time-lapse timeshifts
Measuring time-layse timeshifts
Localizing time-lapse timeshifts
Using time-lapse timeshifts
5.2.4 Time-lapse seismic attributes caused by anisotropic velocity changes
5.2.5 Other time-lapse seismic observations of geomechanical processes
5.3 Prediction of stress-induced seismic attributes
5.3.1 Time-lapse timeshifts for vertical wave propagation
5.3.2 Offset dependence of time-lapse timeshifts and change in P-wave anisotropy
5.3.3 Dependence of overburden time-lapse timeshifts on underburden properties
5.3.4 S-wave splitting as indicator of horizontal stress S-wave splitting in the subsidence bowl at Valhall
Time-lapse S-wave splitting in reservoir
5.3.5 Can VTI anisotropy be negative in a depleted reservoir?
Field observations of negative anisotropy inside a pressure-depleted reservoir
5.4 Conclusion
6 Case Study: 3D Exploration Geomechanical Model
6.1 Abstract
6.2 Introduction
6.3 Building a 3D MEM using 3D seismic inversion models, rock physics and geomechanics
6.3.1 Seismic data acquisition and processing
6.3.2 AVO inversion
Wavelet estimation
Low-frequency model building
6.3.3 Gridded model and time-to-depth conversion
6.3.4 Mechanical properties
6.4 Analysing the geomechanical model
6.4.1 Prediction of fracture location and orientation
6.4.2 Fault control on stress orientation
6.4.3 Near-wellbore stress concentration and rotation
6.5 Discussion
6.5.1 Geomechanical characterization using seismic data only”
6.5.2 Using seismic data to calibrate a 3D mechanical earth model
6.5.3 Iterative mechanical earth models
6.6 Summary
7 Case Study: Joint Interpretation of 4D MEM with Time-Lapse Seismic Data
7.1 Abstract
7.2 Petroleum geology and reservoir production of South Arne
7.3 Time-lapse seismic data: Acquisition, processing and inversion
7.3.1 Acquisition and processing
7.3.2 Time-lapse timeshifts and amplitude changes
7.3.3 Time-lapse AVO inversion
7.4 Application of time-lapse rock physics AVO inversion and time-lapse timeshift observations
7.4.1 Reservoir depletion of the northern crest
7.4.2 Fault control of injected water on the southwest flank
7.4.3 Compaction monitoring on the northern crest
7.5 Discussion
7.6 Conclusion
References
Appendix A: Seismic Velocity in Anisotropic Media
A.1 Isotropic medium
A.2 VTI medium
A.2.1 Wave propagation along symmetry axes
A.2.2 Thomsen parameters
A.3 Orthorhombic medium
A.3.1 Wave propagation along symmetry axes
A.3.2 Tsvankin parameters
A.3.3 Velocity as function of propagation direction
A.4 Velocity calculation using the Kelvin-Christoffel matrix
References
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