GREEN RIVER - With the success of using carbon dioxide to revitalize the century-old Salt Creek oil field in central Wyoming under its belt, Houston-based Anadarko Petroleum Corp. is proposing to use the same technique to coax more oil out of established fields in Sweetwater County.

The Bureau of Land Management recently released its environmental study on the company's proposed Monell Enhanced Oil Recovery Project for public review.

The company is proposing to pump carbon dioxide into its Patrick Draw Field Monell Unit to increase pressure and to push the oil to production wells. Anadarko officials said results from a pilot program in the project area indicated that CO2 flooding would be an effective method of recovering the additional oil remaining in the ground.

The company hopes to recover an estimated additional 28 million barrels of oil using the technique, according to the BLM study.

Enhanced oil recovery typically involves efforts to improve the flow of oil from a reservoir that has already been produced by conventional means. Over time, oil reservoir pressure drops off, and so does the rate of oil production.

Carbon dioxide, in liquid form, mixes with the oil and pushes to production wells. The carbon dioxide can then be separated from the oil and reused, or stored in the oil reservoir so that it is not released into the atmosphere.

The CO2 will be shipped by pipeline and originate from ExxonMobil's Shute Creek gas plant near LaBarge in southwest Wyoming, according to company plans.

The 50-year-old Patrick Draw project area is located immediately south of Interstate 80, about 35 miles east of Rock Springs in southeastern Sweetwater County.

Anadarko is proposing to drill up to 126 enhanced recovery wells - 46 on federally managed public lands, three on state lands and 77 on private lands.

BLM Project Leader Darlene Horsey said the area would be drilled and developed over three to six years. The project will require about 127 miles of access roads and gathering lines.

Oil production in Wyoming has declined at an annual rate of about 5 percent since 1991, according to Wyoming Geological Survey figures. Injection of carbon dioxide to increase oil recovery has been employed since the early 1950s nationwide, but the first commercial application of carbon dioxide flooding in Wyoming was Amoco's Bairoil Project in 1986.

Anadarko is using carbon dioxide flooding in the Salt Creek Field near Midwest in Natrona County. Anadarko paid $265 million for Howell Corp. in 2002 and acquired the 115-year-old landmark Salt Creek oil field.

Southwest Wyoming bureau reporter Jeff Gearino can be reached at 307-875-5359 or at gearino@trib.com.