A slug-type miscible-phase displacement project has been in operation in the 29D pool of the Midway-Sunset field, Kern County, Calif., since March, 1958. This project has resulted to date in the production of 230,000 bbl of additional oil which can be attributed to propane injection. The project is profitable, and the investment was returned in two years. The pool production rate during April, 1960, was 900 B/D, which was 540 B/D more than the previous gas-injection operation. Reservoir pressure is currently about 1,300 psia. The pool now has four injection wells and 12 producing wells, all drilled on 10-acre spacing. To date, a slug of 18 million gal of propane has been injected. Impressive oil stimulation, accompanied by gas-oil ratio reduction, has been observed in most of the first-line wells and several of the second-line wells. Breakthrough of propane occurred in the first-line wells early in the life of the project but has occurred in only one second-line well. Continued production of stimulated wells has shown that additional oil can be recovered after propane breakthrough. The original plan of operations called for injection of a propane slug followed by gas. However, the well's demonstrated ability to produce large quantities of oil after propane breakthrough, and the attendant depletion of the slug, caused the plan of operations to be modified to include recycling of produced propane in a miscible state. Introduction A slug-type miscible-phase displacement project was started in the 29D pool in March, 1958. The pool is located in the Midway-Sunset field about three-miles southeast of Taft, Kern County, Calif. This reservoir was chosen for a miscible-phase displacement secondary recovery program because of the following factors.The quantity of 31°API oil remaining in the reservoir was great enough to make secondary recovery attractive.The pool pressure of 1,500 psia and temperature of 1800° F insured direct miscibility of a propane-injection stream with the reservoir oil.Well configuration and condition and the type of completion were such that good control could be maintained.The production mechanisms were known and understood.The pool size, and the reservoir rock and fluid characteristics were known. Under these circumstances, it was believed the process could work if properly engineered. As of April 1, 1960, the project had paid out and now is operating on a profitable basis.
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Block et al. (1961) studied this question.