TIME LAPSE SEISMIC RESPONSE (4D) RELATED TO INDUSTRIAL-SCALE CO2 INJECTION AT AN EOR AND CCS SITE, CRANFIELD, MS

Reservoir fluid substitution is critical for understanding 4D seismic response. Time lapse seismic surveys have been conducted internationally at well-known field sites like Otway, Weyburn, and Sleipner as well as downhole measurements at Frio and Cranfield in the United States. This project, however, is the first 4D survey conducted in the U.S. for CCS purposes. Continuous CO₂ injection has occurred at an EOR project in Mississippi since 2008, also the location of our SECARB CCS demonstration project funded by DOE’s Regional Carbon Sequestration Partnership. 4D response has been characterized after 3 years of injection, where >3 million tons of CO₂ remain in the subsurface. Results show a definitive but complicated CO₂ response in the injection interval, and no coherent response above or below the injection interval. To further quantify the seismic response, well log data show that V_p decreases before becoming mostly constant, V_s increases linearly, and density slightly decreases in the injection zone. Some areas that have received CO₂ do not have coherent seismic response, indicating that 4D response to injected CO₂ in some parts of the field is masked by residual oil, gas, and brine related to historic production (1960’s). Forward modeling and flow simulation are integrated to understand seismic response in relation to fluid properties and distribution. These results support seismic for reducing CCS risks such as in and out of zone migration and sweep efficiency while benefitting EOR understanding.