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

摘要

The heavy-oil reservoir Bachaquero-01, in the Lagunillasrndistrict of Venezuela’s Lake Maracaibo, has been productivernsince 1934. Because the oil gravity is only 12o API, steam hasrnbeen injected since 1971 to increase production. To furtherrnoptimize production, stand-alone horizontal wells have beenrndrilled since 1996. However, in only 4 months after steam wasrninjected into the horizontal wells, a very fast decline of up torn50% of initial production was observed in these nongravelpackedrnwells.rnIn a drilling-and-completion campaign from October 2000rnto January 2001, 18 horizontal wells were successfully drilledrnand gravel-packed. In this paper we describe the gravel-packrntechniques applied to minimize the rapidly declining rate ofrnproduction in horizontal alternate steam-injection wells. Wernexplain the method used for screen and gravel-size selectionrnand summarize the completion operations and gravel-packrnfluids that were used. We describe the modification of anrnexisting hydraulic packer with a high-temperature seal ofrn600oF—a combination used for the first time worldwide.rnFinally, we illustrate the successful drilling-and-completionrncampaign with case histories and production performance.rnThe gravel-packed wells had an average increase of 15%rnproductivity after 1 year with no sand production. The gravelpackrnoperations were executed at a pump rate of 2 to 3rnbbl/min with a sand concentration of 0.5 to 0.7 pounds ofrnproppant per gallon added (ppa), observing continuous fluidrnreturns of 50% to 80%. The packers were successfully fieldrntested after a period of three weeks of steam injection.