Downhole Water Sink at High Mobility Ratio: The Tambaredjo Field Pilot Test

Abstract

This study discusses the development and results of the Downhole Water Sink (DWS) pilot test in two wells of the Tambaredjo Field (Suriname). It includes the mechanical completion, design and execution of operating strategy, well performance and forecast, and reservoir simulation employing an oil-in-water emulsion formulation. The DWS process, well and reservoir information and properties are introduced. The problem of heavy oil production in oil-water contact (OWC) areas is explained. The results in terms of production data and its analysis, and issues encountered, are presented. A reservoir simulation model capable to handle transport of oil components in water phase is described and used to history-match the production performance. Then, conclusions are drawn from the information presented. Although the water sink is expected to work under stable displacement conditions, the results of the pilot test show that DWS could successfully reduce water coning at the prevalent unstable mobility ratio. It also promoted inverted coning of oil from the transition zone to the water leg completion. This was confirmed by direct measurements of oil content in the fluid produced from the water leg completion. The physical mechanism that allows such phenomenon is hypothesized to be the flow of oil droplets of size smaller than that of the typical pore throat. Such mechanism was numerically modeled and found to be consistent with the pressure and rate measurements at both wells. Early measurement and completion issues in the first well were overcome later on and in the second well. This paper presents the first results for DWS in a heavy oil reservoir with highly adverse mobility ratio. The results will serve as a guidance for implementation of DWS in heavy oil reservoirs overlying an oil-water contact.