Columbia Gas Transmission Corporation, with financial assistance from the U.S. DOE, planned and operated an Enhanced Oil Recovery Project in the Granny's Creek oil field, Clay County, West Virginia. The objective of the field test was to determine the feasibility and economics of recovering additional oil from a (flooded-out) low-oil saturated reservoir using carbon dioxide (CO2) for miscible displacement of residual oil.

The site selected for the test was a 6.7-acre (27,000 m2) portion of a former waterflood pilot test area. The waterflood pilot was highly successful for the area, producing over 4,000 barrels per acre (0.157 m3/m2) over the flood life. The reservoir tested was the Mississippian aged, Pocono Big Injun formation occurring at a depth of 2,000 feet (610 m). Residual oil saturation was approximately 30-35 percent. Porosity averaged 16 percent with an average reservoir permeability of 7 millidarcys.

CO2 injection was initiated in early June 1976. Injection was into four corner wells of a normal five-spot. A center production well and three observation/production wells were also located within the pattern. In the initial test, 10,000 tons (9,070 t) of CO2 was injected into the four wells, employing the WAG injection technique for mobility control. Due to pilot pressure distribution, less than 12 percent of the CO2 entered the pattern. In a second pilot operation phase, a single injection well minitest was initiated within the original CO2 pilot pattern. Over 2,100 tons (1,900 t) of CO2 was injected for this test. Oil production within the pattern during the first phase was over 4,000 barrels (640 m3) with a CO2/oil ratio of 2,500-5,000 scf/bbl (445-890 m3/m3). The minitest produced oil at a 17,337 scf/bbls (3,100 m3/m3) CO2 utilization rate.

Evaluation of the pilot has been most difficult due to complex reservoir heterogeneity and field operation problems. Presently, it does not appear that the CO2 miscible displacement process will be economical for tertiary oil recovery in such low-oil saturation reservoirs without better mobility control for greater sweep efficiency. The test results have determined though, that the CO2 process can mobilize and recover a significant volume of additional oil after waterflooding.

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