Design and Application of an Alkaline-Surfactant-Polymer Recovery System to the West Kiehl Field

Abstract

Summary The West Kiehl Unit, Crook County, Wyoming produces from a Minnelusa Lower "B" Sand reservoir. Original oil in place (OOIP) is estimated at 1,500,000 STBO. Estimated ultimate primary production is 170,000 STBO or 11% OOIP. Four enhanced recovery methods were considered for application in this reservoir. Conventional waterflood, polymer-augmented waterflood, an alkaline-polymer waterflood and an alkaline-surfactant polymer (ASP) flood. Estimated ultimate recoveries are 600,000 STBO (40% OOIP), 600,000 STBO (40% OOIP), 600,000 STBO (40% OOIP) and 855,000 (56% OOIP), respectively. The polymer-augmented flood is expected to deplete the field faster than conventional waterflood with no increase in ultimate recovery, while the ASP process is expected to extend field life and increase ultimate recovery dramatically. The ASP process has been implemented and early performance is very good. Two purposes are being served by implementation of the West Kiehl alkaline-surfactant-polymer flood. First, to recover additional oil, which a waterflood or polymer flood cannot produce. Second, to pilot this potentially significant enhanced oil recovery (EOR) technique for other Minnelusa reservoirs. If this recovery method proves successful it will represent a sizeable increase in ultimate recovery, ranging as high as 15% OOIP. This paper discusses the goals for utilizing an alkaline-surfactant-polymer system at West Kiehl. Further, it details the development of the West Kiehl Field project including laboratory studies, reservoir parameters, initial injection and production history, facilities design, and operations of the flood. Introduction Polymer flooding be an in the Minnelusa trend in 1972 at Stewart Ranch. Mobility control, profile modification, and combination mobility control-profile modification polymer floods have been applied to the Minnelusa fields in secondary and tertiary modes. Polymer can improve sweep efficiency and thereby increase recovery, however it does not reduce residual oil saturation beyond the end point of the water-oil relative permeability curve. Combinations of alkali plus polymer and alkali plus surfactant plus polymer have been shown to reduce the residual oil saturation and thus recover additional oil. Soda Ash (Na CO) plus polymer has improved oil production in the Isenhour Unit, Sublette County, Wyoming and is currently being co-injected in the David Lloydminster A Pool, Alberta, Canada. Caustic Soda (NaOH) plus polymer is being co-injected into the Cessford Pool, Alberta, Canada.