This course reviews the fundamentals of structural geology, continuum mechanics, rock constitutive laws, and applications to fault stability, wellbore stability, hydraulic fracturing and reservoir geomechanics.
This course explores the fundamentals of theoretical geomechanics. Topics include general theory of linear elasticity, plasticity, poromechanics and fracture mechanics. The theory is linked to problems of stability of deviated wellbores, hydraulic fracturing, reservoir depletion, and fault stability.
Review on continuum mechanics: Stresses at a point, principal stresses, Mohr circle, decomposition of the stress tensor and deviatoric stress tensor invariants.
Problems in elasticity: Equilibrium, kinematic, and constitutive laws. Solution of the Navier equations for plane-strain problems. Wellbore problem: determination of in-situ stresses from sonic logs.
Mechanics of the saturated porous solid: Particle fluid interaction, poroelasticity, effective stress, drained and undrained loading, consolidation theory. Problems: overpressure and stress path during reservoir depletion.
Mechanics of open mode fractures: Linear elastic fracture mechanics, PKN-KGD models, wellbore frac tests, hydraulic fracture propagation in heterogeneous media, stress interference in multistage fracturing, open mode fractures in unconsolidated sands. Problem: solve coupled PKN/KGD models.
Mechanical properties of reservoir geomaterials: unconsolidated sands, shale, sandstone, limestone, evaporites, scales and effective properties, heterogeneity-spatial variability, stress-dependent permeability, laboratory methods and measurements.
Table of contents
Week of
Lecture
Literature
Project
1
Introduction to geomechanics in Petroleum Engineering
Espinoza, Ch. 1
–
2
Review Continuum Mechanics: stresses at a point, principal stresses, equilibrium equations, vertical stress. Stress projection on a plane. Stress plotting: Mohr’s circle, stress path, p-q space, I1-J2 space
Fjaer Ch. 1.1
Zoback Ch. 1
Malvern Ch. 2, 3, 4 Jaeger et al. Ch. 2
Espinoza, Ch. 3, 5
(1) Stress tensor profile along a vertical wellbore
(5) Determination of Biot’s coefficient and reservoir stress-path during depletion: CMG verification
8
Undrained loading: consolidation and disequilibrium compaction, Skempton’s coefficient
Fjaer Ch. 1.6
Coussy Ch. 4
Jaeger Ch. 7
9
Thermo-elasticity and visco-elasticity: Thermal stresses around the wellbore and in the reservoir. Long-term reservoir compaction.
Chemo-mechanical coupled processes.
Fjaer Ch. 1.5, 1.9
Coussy Ch. 4
Jaeger Ch. 7.8
Jaeger Ch. 9.8-11
Zoback Ch.3 (end)
10
Inelasticity: fracture modes, shear yield stress: Tresca, von Mises, Drucker Prager, Mohr-Coulomb criterion, the triaxial test.
Fjaer Ch. 2.1, 2.5
Jaeger Ch. 4
Espinoza, Ch. 4
(6) Rock failure and wellbore stability
11
Inelasticity: beyond the yield point, post-peak behavior, flow rule and hardening, critical state soil mechanics, strain-softening and strain-hardening geomaterials, shear-enhanced compaction (compression cap), oedometer test
Fjaer Ch. 2.8
Jaeger Ch. 9
(7) Constitutive models for soft rocks: reservoir ovepressure
12
Mechanics of fluid-driven open mode fractures: tensile strength, breakdown pressure, ideal open-mode fracture propagation, fracture containment
Fjaer Ch. 11
Espinoza, Ch. 7
Final Project: paper abstract due
13
Mechanics of fluid-driven open mode fractures: LEFM, Griffith criterion, fracture toughness, the coupled fluid-driven fracture propagation problem: PKN-KGD models, fracture propagation regimes
Fjaer Ch. 11
Espinoza, Ch. 7
(8) Stress shadows in multistage hydraulic fracturing
14
Mechanics of fluid-driven open mode fractures: microseismicity, open-mode fractures in unconsolidated sediments, multistage hydraulic fracturing design.
Valko and Economides
15
Mechanics of elastic wave propagation, frequency and wavelength, dynamic to static transforms
PGE 373L – Petroleum and Geosystems Engineering Design
There are two equally important goals in this class:
(1) The solution of engineering design problems based on actual field data.
(2) To develop and demonstrate satisfactory written and oral report preparation and delivery skills.
PGE 424 – Petrophysics
This course reviews fundamentals of the physics of rocks, including the measurement of diverse physical properties. The interpretation of measurements and relationship between physical properties is used to assess subsurface resources and processes.
