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Carbon dioxide injection into undersaturated viscous oil reservoirs: simulation and field application

Conference ·
OSTI ID:7214364
This paper provides an analysis of the potential for using carbon dioxide (CO/sub 2/) to increase oil recovery from viscous undersaturated oil reservoirs where the oil zone is underlain by water. The principle role of CO/sub 2/ in this immiscible application is to reduce oil viscosity in order to increase the ultimate oil recovery by reducing water coning. The use of CO/sub 2/ or rich gas for viscosity reduction in heavy undersaturated oil reservoirs has been proposed previously, however, this process has not been recommended for bottom water reservoirs. The results of a single well field pilot test are presented. In this test, a slug of CO/sub 2/ was injected at the oil-water contact. Following a soak period the well was back produced to measure the change in water-oil ratio. The CO/sub 2/ treatment temporarily reduced the water-oil ratio; however, during back production the water-oil ratio increased to above the stabilized pretest value. Several explanations for this behavior are proposed. A numerical single well model in the r-z coordinates with implicit handling of saturation pressure was developed. This model was used to match the CO/sub 2/ test results, to investigate sensitivity of process variables, to predict the performance of a multicycle single well CO/sub 2/ scheme and to investigate other potential CO/sub 2/ recovery schemes for viscous oil bottom-water reservoirs. The model results show that a multi-cycle single well injection-productionscheme is not feasible. On further investigation, a potentially feasible scheme was discovered in which a slug of CO/sub 2/ is injected some distance from the producing well. For the particular case studied, computer model studies indicate a 50 percent increase in oil recovery over the noncarbonated base case.
OSTI ID:
7214364
Report Number(s):
CONF-761008-86
Country of Publication:
United States
Language:
English