Tomographic Inversion and Poroelastic Modeling for Reservoir Characterization

A system for simulation of seismic responses of porous elastic reservoirs has been developed. Simulation involves numerically applying the concepts and techniques of Biot theory to the analysis of behaviors of reservoirs. Tomographic inversion and wavefield imaging were used to provide the prerequisite velocity and structural background, respectively. Then, poroelastic modeling of seismic wave propagation was implemented in the time-space domain with a finite-difference scheme, for comparison with Gulf Coast reservoir data. Results from numerical simulation with Biot theory indicate that porosity has significant effects on wave propagation velocities; viscosity-to-permeability ratio primarily influences amplitudes, but is almost negligible at seismic frequencies. Cross-hole, VSP and surface survey seismograms for Gulf Coast reservoir models contain primary and converted reflections from fluid as well as lithologic contacts, and illustrate the distribution of information available for reservoir description. A major limitation in the classical Biot theory is that attenuation is assumed to be the result only of the relative motion between fluid and solid, and hence on the coupling provided by the viscosity of the fluid. The main enhancements that will overcome this limitation would be direct inclusion of attenuation due to the absolute fluid viscosity and to the anelasticity of the solid frame.