Case History of Steam Soaking in the Kern River Field, California

Abstract

Abstract Crestmont Oil Co.'s 42-acre May Fee property is located in the Kern River field, and consists of eight wells in the China Grade zone and seven wells in the Kern River zone. The average well declined from an initial production of 70 to 4 BOPD in seven years, while recovering only 9 per cent of the oil in place. A thermal recovery program was initiated using the steam soak method of injecting, soaking, and then producing. After injecting an average of 10,000 bbl of water as 80 per cent quality steam in six of the 15 wells, production increased from 1,635 to 13,374 bbl/month. The eightfold increase in production can be accounted for by the fact that these zones are ideally responsive to steam stimulation, due to the large decrease in viscosity realized by small increases in temperature and the large amount of 12.5 deg. gravity oil remaining at relatively shallow depths. Introduction Primary production from the seven- and 15-year-old wells on the 42-acre property had declined to 2 to 6 BOPD/well, even though only 9 per cent of the original oil in place had been produced. Late in 1962 Crestmont Oil Co. decided to investigate various methods of thermal recovery to see if the remaining oil could be economically recovered. The purpose of this paper is topresent the reservoir conditions prior to steam injection,describe equipment used and the method of injection,tabulate the results before and after the wells were steamed, andtabulate techniques and conclusions regarding steam injection. Geological Description The Kern River zone contains 190 net ft of oil sand from 700 to 1,000 ft. There are several strata of shale throughout the zone, with a 60-ft interval occurring at 850 ft. The formation has 35 per cent porosity, 20 per cent connate water, and a 1.05 formation volume factor. The viscosity of the oil at the ambient reservoir temperature of 80F is 7,000 Saybolt-seconds. The gravity averages 12.6 at 60F. The Kern River zone contains approximately 1,900 bbl of oil/acre-ft. A zone of fresh water, identical to the produced water, exists from just below the surface to the top of the Kern River zone. Fig. 1 shows a composite log of the Kern River and China Grade zones. The China Grade zone contains 20 ft of oil sand in Te 35 ft from 1,200 to 1,235 ft. The China Grade zone exhibits a more uniform vertical homogeneity than the Kern River zone. The ambient temperature, viscosity and gravity are closely related to the Kern River zone. JPT