In early 1985 Chevron U.S.A. initiated a pilot steamflood of the light 27°API gravity (0.89-g/cm3) crude in the 108-ft (32.9-m) thick Wilhelm sand reservoir at the Buena Vista Hills Field in Kern County, California. The pilot project involves 12 inverted five-spot patterns over a 65-acre (263,000-m2) area with the target reservoir at an average depth of 2500 ft (762 m). A computer simulation study was performed to provide performance forecast and other information useful for the design, implementation, and operation of this first application of steamflooding to a light oil reservoir by Chevron.

A one-eighth of a five-spot, three-dimensional representation of the reservoir was simulated using a compositional steamflood simulator. The reservoir oil was represented by a three pseudo component model based on a true boiling point curve analysis of the crude.

The study showed that because of the low viscosity and high volatility of the oil, steamflooding this oil benefits from mechanisms different than those for a heavy oil. While oil viscosity reduction is the primary mechanism for production of a heavy oil, steam distillation is shown to be mainly responsible for improved production from the light oil reservoir. Whereas gravity override of steam prevails in a heavy oil reservoir, steam is seen to propagate in a more piston-like manner in the light oil reservoir, producing a more effective sweep of the reservoir. Also, the steamflooding in the low compressibility, light oil reservoir is characterized by an almost immediate production response to steam injection.

The study further showed that approximately 50% of the oil initially in place can be recovered economically by steamflooding. Over one-third of this recovery can be attributed to the steam distillation mechanism.

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