Based On The Theory Of Fracture Media Co < Sub > 2 < / Sub > Geologic Sequestration Of 4 D Avoa Is Inversion

CCS (Carbon capture and sequestration) technique now is playing a critical role on reducing Green house effects. CO2geological storage, the most crucial issue, however, is how to observe, monitor and confirm that CO2is safely sealed without leakage in geological setting such as aquifer, oil and gas reservoir and other rocks with rich porosity in the future of200-1000years. In general,4D seismic monitoring or time-lapsed seismic method becomes a necessary process for security of CCS. Time-lapse seismic response difference can be divide into two categories:Time-shift analysis and amplitude analysis.This thesis raise a issue on amplitude difference analysis for Weyburn4D seismic data. At present, the post-stack seismic amplitude difference analysis is mainly used to determine the scope of the general distribution of CO2. Seismic amplitude difference of stacked section is mainly due to the saturation and pressure effects of reservoir. Time-lapse AVO technique utilize AVO gradient&intercept crossplot to identify the spatial distribution of saturation and pressure of CO2more accurately.However, the current4D AVO analysis is essentially based on the theory of porous media and isotropic medium, which does not consider the fracture-induced anisotropy when CO2is injected into reservoir. In this study, a four-dimensional seismic data in the Weyburn field in Canada is reprocessed rely on amplitude preserving technique by Promax, and also I developed a new method for prestack amplitude calibration. Most importantly, I carry on a time-lapse azimuth AVO analysis base on Hudson’s crack media theory, to some degree, which is more realistic for Weyburn field reservoir.In summary, time-lapse azimuth AVO analysis for Weyburn field data shows that AVOA curve of year1999dataset could be distinguished from that of year2002. The difference also can be identified in the AVO gradient&intercept crossplot with different azimuth. The time-lapse amplitude difference of top Marly is mainly due to the increasing of CO2saturation and pressure. However, fracture-induced anisotropy, which is enhanced by pore pressure, is playing the leading role in azimuthal AVO characterization.