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 sequestration and monitoring process, based on an idealized geologic model of the Sleipner field. First, we simulated a constant-rate injection into the idealized geologic model to study the basics of the two-phase flow involved in sequestration. The main features of the plume evolution and pressure build-up are captured in the simulation results. In any sequestration project, an important part is monitoring distribution using seismic methods. The seismic response of the injected is controlled by its effect on elastic properties of the reservoir rock. We built a rock-physics model to assess the effect of on wave properties. For unconsolidated sand, a sensitivity study found that 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 , and the seismic response of is strong enough to be resolved from seismic data.