Although many field tests since 1964 have demonstrated that CO2 is an efficient oil recovery agent, field-wide applications of CO2 injection have been rare becauselarge quantities of CO2 were not readily available at reasonable cost. A large supply of CO2 at a suitable price is nowavailable to West Texas oil fields, and plans are being made to provide similar supplies to oil fields in the Williston Basin, North Dakota, California and Colorado. As a result, many field applications are being planned in the United States and some are underway.

The authors discuss the response of CO2 to prevailing reservoir conditions which determine whether the flood will be miscible or immiscible. They conclude that reservoir pressure, temperature and oil composition are primary factors in determining how efficient the oil recovery will be. The authors discuss the laboratory tests used to define the optimum operating conditions and any deleterious effects from combining CO2 and oil (such as asphaltene or wax precipitation), the importance of developing an accurate reservoir description, and whether or not WAG (water alternated with gas) should be used to improve the recovery of oil by the process. Other techniques to control channeling of the injected CO2 and improve its sweep efficiency are also discussed.

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