1. Structural Analysis of Fractured Hydrocarbon Reservoirs: Role of Rock Rheology Seth Busetti University of Oklahoma November 2008

2. 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 Simple Uses only Geometry Simple Computation Valid for Small Strain

3. Deformation of Rock Layers Four main stages of rock deformation Mt. Scott Granite (Katz and Reches, 2004) Crack/pore closure Linear Elastic Stage Damage by Microcracking [Strain Hardening] Extensive Damage, Crack Coalescence Macroscopic Fracturing

4. Mechanical Simulations of Structures Physical ObservationsMathematical Expression Structure Layering Folds Faults/Fractures Geologic Features Ramps, pins, blocks Layer Friction Stress Conditions Tectonic Stress Local Stress Rock Mechanics Properties Elasticity Plasticity Failure Porosity/Permeability Numerical Method Geometry Discretization (nodes/elements) Discontinuities Boundary Conditions Degrees of Freedom Penalty Contact Loading Conditions Surface Pressure Point/surface Loads *Rock [Material] Rheology Material Model Parameters σ-ε curve u1xu1yu1xu1y u2xu2yu2xu2y u3xu3yu3xu3y u4xu4yu4xu4y [K e ] [K]{u}+[M]{a}+[C]{v} = {f} {f} Ellenberger Limestone Barnett Siliceous Shale Barnett Mudstone Barnett Calcareous Mudstone Berea Sandstone Indiana Limestone Preliminary Material Modeling: Calibration / Benchmark Testing

5. Deformation of Rock Layer: 4-Point Beam Berea Sandstone Rheology: Elastic-Plastic with Damage Onset of Damage [Plasticity] Stiffness Degradation Failure [Fracture] Piston Down 10 MPa Confining Pressure [Triaxial] Beam Loading Piston Load Cell Confining Pressure

6. Deformation of Rock Layer: 4-Point Beam Berea Sandstone Rheology: Elastic-Plastic with Damage

7. Large-Scale Deformation Application Mohr-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

8. 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