ESTIMATION OF EFFECTIVE PRESSURE AND WATER SATURATION BY VISCOELASTIC INVERSION OF SYNTHETIC TIME-LAPSE SEISMIC DATA FOR A GAS SANDSTONE RESERVOIR

摘要

Inversion of synthetic seismic data for a viscoelastic reservoir model provides estimates of changes in effective pressure (P_e) and water saturation (S_w) over time. Application is to analysis of simulated time-lapse seismic data for a gas sandstone reservoir. Estimation of unique values of P_e and S_w from two independent seismic data [such as P-wave velocity (V_p) and S-wave quality factor (Q_s)] is theoretically feasible, if the other reservoir properties are known. In the S_w-P_e plane, the solution corresponds to a point for noise-free data and a region for noisy data. For the reservoir properties [porosity (φ), clay content, permeability (k)], and the dominant seismic frequency (40 Hz) used in the synthetic examples, density, Q_s and Q_s/Q_p are primarily dependent on S_w, V_p is primarily dependent on P_e, and V_s, Q_p and V_p/V_s are dependent on both S_w and P_e.