Water-Alternating-Steam Process Improves Project Economics at West Coalinga Field

Abstract

Summary The water-alternating-steam process (WASP) was applied to vertical expansion (VE) sands in the pilot area of Section 13D, West Coalinga field to stop wasteful steam production and to improve vertical conformance of injected steam. Before the WASP application, steam breakthrough in the VE sands caused well sanding, cutting of downhole tubulars, and high-temperature-fluid handling problems. To alleviate these problems, pumps had to be raised in five wells and one well had to be shut in, reducing oil production from the VE sands and the lower waterflooded zones. A WASP field test, based on a numerical simulation study, was implemented in July 1988 with alternating slugs of water and steam, each injected over 4 months. The WASP eliminated steam production, allowing the pumps to be lowered and the one shut-in well to return to production. Oil production remained constant through the first WASP cycle and increased during the second cycle. Sales oil (total production minus oil used to generate steam) increased as a result of saving generator fuel during the water leg of each WASP cycle, resulting in improved project economics.