It is estimated that there are 85-110 billion barrels of heavy oil reserves in the U.S.. Since the 1960's, steam has been the predominant Enhanced Oil Recovery (EOR) method for these high viscosity, heavy oil reservoirs worldwide. However, some experimentation utilizing immiscible carbondioxide injection in heavy oil reservoirs has shown encouraging results. This paper documents the efforts of a 2-1/2 year, two phase project conducted in the Midway-Sunset field of California applying a novel steam/carbon-dioxide combination process to recover heavy oil.

In many instances in thermal recovery projects, steam channeling and/or steam override reduces the efficiency of the process. This inefficiency has been corrected, or at least somewhat mitigated, through the use of steam foams. A cost effective alternative to foams was developed as part of the research phase of this project. A high temperature, stable polymer gel/surfactant solution has been developed and has proven in field tests to be extremely effective at diverting steam from steam channels and the override zone to areas of the reservoir higher in oil saturation. By accomplishing this diversion, it allowed carbon-dioxide, injected along with the steam, to enter a potentially more productive portion of the reservoir. During the 2-1/2 years of the project, nine cyclic steam stimulation wells and two continuous steam drive injection wells were treated with the novel EOR process.

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