Seismic reflection data processing of 3D surveys over an EOR CO2 injection

Abstract

In this project three 3-D reflection seismic surveys were analyzed with respect to pre and post stack reflection processing steps that resulted in the identification of a possible pre-stack seismic attribute proxy for subsurface supercritical CO2. The project was part of the Bureau of Economic Geology collaboration with the National Energy Technology Laboratory of the United States Department of Energy and the Bureau of Economic Geology as part of a Southwest Regional CO2 Sequestration Partnership. A variety of processing techniques were used to calculate seismic attributes and invert the seismic post stack seismic data to determine acoustic impedance. Methodologies for acoustic impedance inversion included Model-based inversion, bandwidth limited inversion, colored inversion, sparse spike, and neural network. In addition, pre-stack amplitude variation with offset (AVO) analysis was completed using second order polynomial, third order polynomial, Shuey 2-term, Shuey 3-term, linear, Verm-Hilterman, Aki-Richards 2-term and Aki-Richards 3-term methods. Using a combination of Shuey 3-term coefficients we believe that we have identified a useful proxy for monitoring subsurface CO2. In our analysis the attribute anomaly variation proxy is spatially located above brine fluid, flat bottomed and appears to be pore-phase variation. It follows reasonable trapping geometries and appears to be linked with possible earlier CO2 injection sites.