LPG-Gas Injection Recovery Process Burkett Unit, Greenwood County, Kansas

Abstract

WIEMER, R.F., PHILLIPS PETROLEUM CO., BARTLESVILLE, OKLA. Abstract Many properties throughout the country have been depleted by waterflood operations, and many other such operations are approaching their economic limit. These properties generally contain, after depletion by flooding, another volume of oil equal to that produced by both primary and secondary operations. Laboratory investigations of the LPG-Gas Injection Recovery Process indicated that the process could be applied economically as a tertiary method of oil recovery following secondary water flood operations. The large reserve remaining after flooding prompted a field test of LPG gas injection to determine the volume of remaining oil that could be recovered, and whether the process could be applied economically on a larger scale. The area selected for the pilot test was a 10-acre tract on the Phillips- operated Burkett unit, Greenwood County, Kans. The performance of the input and producing wells in the test tract during the course of waterflooding was normal, with no indication of anomalies in the sand body causing channeling or by-passing. At the start of the LPG-gas injection test, it was estimated that the residual oil saturation in the 10-acre tract amounted to 63,250 bbl. A total of 18,131 bbl of LPG, 90 to 95-per cent propane, followed by 67,946 Mcf of dry gas, was injected into the centrally located input well. Water injection was resumed following the LPG-gas injection period. Additional oil recovered, as a result of the test. amounted to 12,120 bbl as compared to the 18,131 bbl of LPG injected. The results indicate that an oil bank can be formed in a watered-out reservoir, and additional oil recovered by this process; however, the volume of additional oil recovered from this particular test was insufficient to indicate that the process could be applied economically. Introduction In recent years there has been considerable interest in the industry regarding the injection of LPG, followed by gas, into oil reservoirs to increase the ultimate recovery. Laboratory investigations, while most often dealing with the recovery process as applied to primary oil reservoirs, indicated that the LPG-gas injection process could also be applied economically as a tertiary method of oil recovery following secondary waterflood operations. With laboratory tests indicating that increased recovery could be realized, a field test was dictated to determine the practical value of the process in field operations. Phillips Petroleum Co. and many other operators have numerous waterfloods throughout the mid-continent area which are reaching their economic limit. On the average, these projects have recovered by waterflood operations a volume of oil equal to that produced under primary operations. It is well known, however, that these same properties generally contain, after depletion by flooding, another' volume of oil equal to that produced by both primary and water- injection operations. It was this large, attractive reserve that prompted Phillips and its partners to undertake a field test of LPG-gas injection to determine the volume of remaining oil, following waterflood operations, that could be recovered, and whether the process could be applied economically on a larger scale. Burkett Unit History The area selected for the pilot test was a 10-acre tract on the Burkett unit, Greenwood County, Kans. The unit, Fig. 1, with the exception of a few wells, covers the entire Burkett pool of approximately 1,040 acres, and is representative of many properties in Eastern Kansas which have reached marginal status under waterflood operations. The pool, discovered in 1922, produces from the Bartlesville sand at a depth of some 2,100 ft. This is a typical "shoe-string" sand in the Cherokee shale of Pennsylvanian age. The reservoir is an elongated, narrow sand body, approximately 3 1/2 miles long and 1 mile wide, lenticular in cross section, with an average thickness of 30 ft. Primary oil production reached a peak in 1924, with a yield of 798,944 bbl, an average of 2,180 BOPD. Thereafter, production declined normally over the years. In 1938, production amounted to some 170 BOPD. from 87 wells still producing. and the pool was depleted under primary operations. Unitization of working interest, to conduct secondary recovery operations, was effected on Jan. 1. 1939, with Phillips as operator and five major oil companies (Marathon. Mobil, Cities Service, Sunray DX and Pure) and three individuals as participants. JPT P. 1067^