Process Modeling of CO 2 Injection into Natural Gas Reservoirs for Carbon Sequestration and Enhanced Gas Recovery

Injection of CO 2 into depleted natural gas reservoirs offers the potential to sequester carbon while simultaneously enhancing CH 4 recovery. Enhanced CH 4 recovery can partially offset the costs of CO 2 injection. With the goal of analyzing the feasibility of carbon sequestration with enhanced gas recovery (CSEGR), we are investigating the physical processes associated with injecting CO 2 into natural gas reservoirs. The properties of natural gas reservoirs and CO 2 and CH 4 appear to favor CSEGR. To simulate the processes of CSEGR, a module for the TOUGH2 reservoir simulator that includes water, brine, CO 2, tracer, and CH 4 in nonisothermal conditions has been developed. Simulations based on the Rio Vista Gas Field in the Central Valley of California are used to test the feasibility of CSEGR using CO 2 separated from flue gas generated by the 680 MW Antioch gas-fired power plant. Model results show that CO 2 injection allows additional CH 4 to be produced during and after CO 2 injection.