Application of extended elastic impedance in seismic geomechanics

We have evaluated an innovative application of extended elastic impedance (EEI) to integrate seismic and geomechanics for geomechanical interpretation of hydrocarbon reservoirs. EEI analysis is used to extract geomechanical parameters. To verify and assess the capabilities of EEI analysis for extracting geomechanical parameters, we selected a jointed, oil-bearing, shale carbonate reservoir in the southwest of Iran, and we used petrophysical data and core analysis to estimate static and dynamic moduli of the reservoir rock. We calculated the corresponding EEI curve to different intercept-gradient coordinate rotation angles (the chi angle, chi), and we selected the angles of the maximum correlation for the corresponding geomechanical parameters. Then, combining the intercept and gradient, we generated 3D reflectivity patterns of EEI at different angles. To obtain a cube of geomechanical parameters, we performed model-based inversion on the EEI reflectivity pattern. A comparison between the modeling results and well data indicated that the geomechanical parameters estimated by our method were well-correlated to the observed data. Accordingly, we extracted the geomechanical and rock-physical parameters from the EEI cube. We further found that EEI analysis was capable of giving a 3D mechanical earth model of the reservoir with the appropriate accuracy. Finally, we verified the proposed methodology on a blind well and compared the results with those of the simultaneous inversion, indicating comparable levels of accuracy. Therefore, application of this method in seismic geomechanics can bring about significant progress in the future.