Time-lapse pre-stack seismic inversion with thin bed resolution for CO2 sequestration from Cranfield, Mississippi

Abstract

Time-lapse surface seismic surveys have been used for CO2 sequestration monitoring at Cranfield, Mississippi. The 3D time-lapse seismic data were recorded both before (2007) and after (2010) CO2 injection. The injection interval is the lower Tuscaloosa sandstone formation, which appears as a thin layer and displays weak signature due to CO2 injection in the post-stack seismic amplitudes. Previous studies have reported inversion of time-lapse acoustic impedances for CO2 plume mapping. However, the acoustic impedances lack elastic information, which are more sensitive to the fluid variation. To address this, we applied a basis pursuit pre-stack inversion on time-lapse Amplitude Versus Angle (AVA) datasets to obtain elastic properties (Vp, Vs, density and Vp−Vs ratio). The inverted elastic properties show improved resolution and provide reasonable fits to the well-log data. The temporal changes of inverted elastic properties provide a basis for mapping the CO2 plume after three years’ injection, demonstrating their effectiveness for a CO2 sequestration study.