Water Separation From Wellstream in Inclined Separation Tube With Distributed Tapping

Summary This paper describes observations on water separation from well-stream in an inline separator using the concept of distributed water withdrawal from an inclined tube section. The physical observations were conducted in a laboratory using a 7-in. observation section applying flow rates compatible to North Sea single-well rates. The distributed water withdrawal is achieved by placing a set of evenly spaced tapping points at the bottom of the tube section with facilities to control tapping rates. The observations were made in connection with a joint-industry project to validate and commercialize a new concept for downhole and seabed separations. The driver for the study is to verify possible water separation by distributed tapping from the bottom of the tube in high flow rates with a high degree of agitation, turbulence, and phase dispersion. Observations demonstrated that for a wide range of flow, comparable to the flow conditions in high-rate oil wells, the high turbulence and phase dispersion do not erode and disperse completely a continuous layer of water on the bottom of the tube. This layer, flowing upward or downward depending on the flow conditions, facilitates a reasonable water separation when it is tapped properly. The scope of the test intended to capture the effect of flow and system variables on the separation efficiency. The experiments and the analysis validated the distributed separation concept. They demonstrated good separation at a wide range of flow stream conditions. They explained the reasons for good separation even with a high degree of turbulence and phase dispersion. The mechanistic understanding of the separation allows a degree of predictability and guidance for separator design.