Results of Thermal Horizontal Completions with Sand Control in Lake Maracaibo, Venezuela: Case Histories of Horizontal Gravel Packs in Bachaquero-01 Reservoir

Abstract

Abstract The heavy-oil reservoir Bachaquero-01, in the Lagunillas district of Venezuela's Lake Maracaibo, has been productive since 1934. Because the oil gravity is only 12° API, steam has been injected since 1971 to increase production. To further optimize production, stand-alone horizontal wells have been drilled since 1996. However, in only 4 months after steam was injected into the horizontal wells, a very fast decline of up to 50% of initial production was observed in these nongravel- packed wells. In a drilling-and-completion campaign from October 2000 to January 2001, 18 horizontal wells were successfully drilled and gravel-packed. In this paper we describe the gravel-pack techniques applied to minimize the rapidly declining rate of production in horizontal alternate steam-injection wells. We explain the method used for screen and gravel-size selection and summarize the completion operations and gravel-pack fluids that were used. We describe the modification of an existing hydraulic packer with a high-temperature seal of 600°F—a combination used for the first time worldwide. Finally, we illustrate the successful drilling-and-completion campaign with case histories and production performance. The gravel-packed wells had an average increase of 15% productivity after 1 year with no sand production. The gravel- pack operations were executed at a pump rate of 2 to 3 bbl/min with a sand concentration of 0.5 to 0.7 pounds of proppant per gallon added (ppa), observing continuous fluid returns of 50% to 80%. The packers were successfully field tested after a period of three weeks of steam injection.