Vertical Interference Test in Wells With Downhole Water Sink Completions

Downhole water sink (DWS) well completions segregate production in the wellbore by producing water from the underlying aquifer and oil—from the oil zone of the reservoir. A pump drains water from the bottom completion to create a pressure drawdown that prevents water from coning up to the top, oil producing zone. Successful application of DWS technology in wells with water-coning problem requires effective isolation between the top and bottom completions of the well. Since DWS technology requires dual completion, the completion is configured for vertical interference testing. The problem is that such test involves flow of two fluids, water and oil. This paper presents a new mathematical model and analysis method for vertical interference testing using top completion (in the oil leg) for production and bottom completion (in the water leg) for observation. The model is analytical and accommodates partial penetration and permeability anisotropy. The analysis method employs a family of type-curves. Examples of possible applications of this new testing method are also shown in this paper.