Constraining the reservoir model of an injected CO2 plume with crosswell CASSM at the Frio-II brine pilot

Abstract

Crosswell CASSM (continuous active-source seismic monitoring) data was acquired as part of the Frio-II brine pilot CO2 injection experiment. To gain insight into the CO2 plume evolution, we have integrated the 3D multiphase flow modeling code TOUGH2 with seismic simulation codes via a petrophysical model that predicts seismic velocity for a given CO2 saturation. Results of forward seismic modeling based on the CO2 saturation distribution produced by an initial TOUGH2 model compare poorly with the CASSM data, indicating that the initial flow model did not capture the actual CO2 plume dynamics. Updates to the TOUGH2 model required to better match the CASSM field data indicate vertical flow near the injection well, with increased horizontal plume growth occurring at the top of the reservoir sand. The CASSM continuous delay time data are ideal for constraining the modeled spatiotemporal evolution of the CO2 plume and allow improvement in reservoir model and estimation of CO2 plume properties.