The 232-mile Greencore pipeline is once again under construction north of Casper and headed toward Campbell County and north to Montana's Bell Creek field.

The 20-inch pipeline will carry carbon dioxide from ConocoPhillips' gas plant at Lost Cabin in eastern Fremont County. Greencore is a subsidiary of Denbury Resources, headquartered in Plano, Texas. The CO2 will also be used in the Cedar Creek Anticline field.

Carbon dioxide is injected into mature oil and gas fields to enhance recovery of oil that might otherwise be left in the ground. Anadarko Petroleum has been highly successful at stimulating new production at the 100-plus year old Salt Creek oil field at Midwest-Edgerton. Denbury has used carbon dioxide in a Mississippi field that now accounts for 50 percent of that state's oil production, according to Bob Cornelius, Denbury's senior vice president for CO2 supply in an earlier interview.

The Greencore pipeline will cost an estimated $275-$325 million to complete. The pipe has been made in Greece and shipped to Wyoming via cargo ships and rail. Construction started in August 2011 but ceased in November. The federal government only allows construction between August and November in the name of wildlife protection. The contractor on this year's work is Sunland Construction out of New Mexico. That entity replaced Rockford Construction, which did last year's part of the project.

Denbury/Greencore has also received approval from the Bureau of Land Management for a second CO2 pipeline that will be used to enhance oil recovery from the Grieve oil field in western Natrona County. Denbury is half-owner of the field, with Elk Petroleum of Australia. The company hopes to extract an additional 24 million barrels of oil from the old field. The three-mile Grieve field line will be under construction this fall.

Proponents of using CO2 as an enhanced oil recovery (EOR) tool point to the obvious benefit of the so-called greenhouse gas being permanently sequestered in the ground when it is used to push additional oil out of old wells. The Greencore line has a capacity of more than 700 million cubic feet of CO2 a day.

Pipeline construction will result in more than 200 jobs in the Casper area. The international engineering firm CH2MHill is the project inspector. The company rents the former F.A.A. Flight Service Station at Casper/Natrona County International Airport. Sunland also rents equipment storage areas at the airport and hauls employees between the airport and job site.

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