ABSTRACT

CO2 capture and sequestration is a promising approach to reduce carbon emission and mitigate the greenhouse effect. We have developed a methodology combining reservoir simulation, rock-physics theory, and seismic modeling to simulate the CO2 sequestration and monitoring process, based on an idealized geologic model of the Sleipner field. First, we simulated a constant-rate CO2 injection into the idealized geologic model to study the basics of the two-phase flow involved in CO2 sequestration. The main features of the CO2 plume evolution and pressure build-up are captured in the simulation results. In any CO2 sequestration project, an important part is monitoring CO2 distribution using seismic methods. The seismic response of the injected CO2 is controlled by its effect on elastic properties of the reservoir rock. We built a rock-physics model to assess the effect of CO2 on wave properties. For unconsolidated sand, a sensitivity study found that CO2 saturation and effective pressure can strongly affect wave properties. Based on the reservoir simulation results and the rock-physics model, seismic modeling is performed at different stages of the injection using the symplectic stereomodeling method. The synthetic seismograms found that the seismic responses of the reservoir are strongly affected by the saturation and pressure change induced by the injection of CO2, and the seismic response of CO2 is strong enough to be resolved from seismic data.

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