REACTIVE MULTIPHASE BEHAVIOR OF CO2 IN SALINE AQUIFERS BENEATH THE COLORADO PLATEAU

Gas reservoirs developed within the Colorado Plateau and Southern Rocky Mountains region are natural laboratories for studying the factors that promote long-term storage of CO{sub 2}. They also provide sites for storing additional CO{sub 2} if it can be separated from the flue gases of coal-fired power plants in this part of the U.S.A. These natural reservoirs are developed primarily in sandstones and dolomites; shales, mudstones and anhydrite form seals. In many fields, stacked reservoirs are present, indicating that the gas has migrated up through the section. There are also geologically young travertine deposits at the surface, and CO{sub 2}-charged groundwater and springs in the vicinity of known CO{sub 2} occurrences. These near-surface geological and hydrological features also provide examples of the environmental effects of leakage of CO{sub 2} from reservoirs, and justify further study. During reporting period covered here (the first quarter of Year 3 of the project, i.e. October 1-December 31, 2002), the main achievements were: (1) Planning workshop for project participants as well as other Utah researchers involved in CO{sub 2} projects (22 October, 2002), and Utah Geological Survey, Salt Lake City; (2) Presentation of paper to special CO{sub 2} sequestration session at the Geological Society of America Annual Meeting, Denver, 29 October, 2002; (3) Presentation of paper to special CO{sub 2} sequestration session at the Fall Meeting of American Geophysical Union, San Francisco, 10 December, 2002; (4) Identification of dawsonite (sodium-aluminum carbonate) as a late stage mineral deposited in CO{sub 2} feedzone at Springerville, Arizona; (5) Successful matching of known physical constraints to flow beneath the Hunter cross section being used to simulate the effects of CO{sub 2} injection. In about 1000 years, most injected CO{sub 2} may be lost to the surface from the three shallowest reservoirs considered, assuming no reactive processes; and (6) Inclusion of reactive processes in numerical simulations, and indication that CO{sub 2} is sequestered for at 1000 years in form of dissolved CO{sub 2} and carbonate mineral precipitation