Testing CO₂-Foam for Mobility Control at Rock Creek

This paper reports the objectives, design and progress of a field test of "CO₂-foam" as a lowered mobility displacing fluid. It includes the background of mobility control considerations leading to the trial, and describes the influence on it of various operational conditions and constraints. The Rock Creek oil field of Roane County, West Virginia, has been produced since 1906 from a low permeability sandstone with high clay content, and is now near the end of economic life. The area utilized in this test is a smaller portion of two ten-acre five-spots that have been subjected to a conventional CO₂ flood and subsequent waterflooding, in addition to gas recycling and primary production. A major goal of the test was to determine whether the oil remaining in this area could be displaced by a slug of thickened CO₂ to form a mobile oil bank that could be detected at a nearby observation well. A second goal was to test the injectivity of CO₂-foam as liquid CO₂ and dilute surfactant solution were pumped simultaneously down fiberglass tubing into the injection well. The design of the test was based on published measurements of the ability of the chosen surfactant (Alipal CD128) to form a foam-like dispersion with liquid CO₂, on stability at reservoir temperature (73°F; 23°C), on the extent of adsorption onto the reservoir rock, and on the appropriate values of the relative mobility of the CO₂-foam (0.2 cp^-1). Although it has been possible to inject the target quantity of CO₂ foam, the injection of chase water has not yet been completed.