structural analysis of fractured hydrocarbon reservoirs: role of rock rheology seth busetti...
Post on 12-Jan-2016
219 Views
Preview:
TRANSCRIPT
Structural Analysis of Fractured Hydrocarbon Reservoirs:
Role of Rock Rheology
Seth BusettiUniversity of Oklahoma
November 2008
Understanding Rock Deformation
Sanders et al., 2004
Lacazette, 2000
Maerten and Maerten, 2006
Analog Experiments
Kinematic Restoration / Forward Modeling
Linear Elastic Modeling
Mechanical Simulation
Relatively SimpleUses only Geometry
Simple ComputationValid for Small Strain
Deformation of Rock LayersFour main stages of rock deformation
Mt. Scott Granite
(Katz and Reches, 2004)
Crack/pore closure
Linear Elastic Stage
Damage byMicrocracking [Strain Hardening]
Extensive Damage,Crack Coalescence
Macroscopic Fracturing
Mechanical Simulations of StructuresPhysical Observations Mathematical ExpressionStructure
LayeringFoldsFaults/Fractures
Geologic FeaturesRamps, pins, blocksLayer Friction
Stress ConditionsTectonic StressLocal Stress
Rock Mechanics PropertiesElasticityPlasticityFailurePorosity/Permeability
Numerical MethodGeometry
Discretization (nodes/elements)Discontinuities
Boundary ConditionsDegrees of FreedomPenalty Contact
Loading ConditionsSurface PressurePoint/surface Loads
*Rock [Material] Rheology Material Model Parameters σ-ε curve
u1x
u1y
u2x
u2y
u3x
u3y
u4x
u4y
[Ke]
[K]{u}+[M]{a}+[C]{v} = {f}
{f}
Ellenberger LimestoneBarnett Siliceous ShaleBarnett MudstoneBarnett Calcareous MudstoneBerea SandstoneIndiana Limestone
Preliminary Material Modeling: Calibration / Benchmark Testing
Deformation of Rock Layer: 4-Point BeamBerea Sandstone Rheology: Elastic-Plastic with Damage
0 0.001 0.002 0.0030.0E+00
2.0E+06
4.0E+06
6.0E+06
8.0E+06
1.0E+07
1.2E+07
1.4E+07
1.6E+07
1.8E+07Differential σ vs. Axial ε
Strain
Diffe
renti
al S
tres
s
Onset of Damage [Plasticity]
Stiffness Degradation
Failure [Fracture]
Piston Down
10 MPa Confining Pressure [Triaxial]
Beam
Loading Piston
Load CellConfining Pressure
Deformation of Rock Layer: 4-Point BeamBerea Sandstone Rheology: Elastic-Plastic with Damage
0.00E+00 1.00E-02 2.00E-02 3.00E-02 4.00E-02 5.00E-02 6.00E-02 7.00E-02 8.00E-020.00
0.02
0.04
0.06
0.08
0.10
0.12
0.14
0.16
0.18
0.20 Fracturing Stage
Coalescence
Microcracking Stage
Elastic Stage
Damage Before Failure
Distance from Center (m)
d2y/
dx2
Large-Scale Deformation ApplicationMohr-Coulomb Rheology
20,000 m
10,000 m
Open Questions:Damaged Shear Zones vs. Fault Planes?Mechanisms for Fault Rotation?Role of Footwall Deformation?
Chimney and Kluth, 2002
Summary
Rheology strongly effects rock deformation
Deformed rocks contain pervasive damage
Damaged layers frequently behave plastically
A Mechanical approach may be necessary to understand many reservoirs, especially where fractures and faults are prevalent
Numerical (i.e., finite element) techniques are a powerful tool for analyzing complex reservoir structures using realistic mechanics
top related