Lawrence Berkeley National Laboratory

WESTCARB, one of seven U.S. Department of Energy partnerships, identified (during its Phase I study) over 600 gigatonnes of CO2 storage capacity in geologic formations located in the Western region. The Western region includes the WESTCARB partnership states of Alaska, Arizona, California, Nevada, Oregon and Washington and the Canadian province of British Columbia. The WESTCARB Phase II study is currently under way, featuring three geologic and two terrestrial CO2 pilot projects designed to test promising sequestration technologies at sites broadly representative of the region's largest potential carbon sinks. This paper focuses on two of the geologic pilot studies planned for Phase II -referred to-collectively as the Rosetta-Calpine CO2 Storage Project. The first pilot test will demonstrate injection of CO2 into a saline formation beneath a depleted gas reservoir. The second test will gather data for assessing CO2 enhanced gas recovery (EGR) as well as storage in a depleted gas reservoir. The benefit of enhanced oil recovery (EOR) using injected CO2 to drive or sweep oil from the reservoir toward a production well is well known. EaR involves a similar CO2 injection process, but has received far less attention. Depleted natural gas reservoirs still contain methane; therefore, CO2 injection may enhance methane production by reservoir repressurization or pressure maintenance. CO2 injection into a saline formation, followed by injection into a depleted natural gas reservoir, is currently scheduled to start in October 2006.