This paper was prepared for presentation at the 1999 SPE Annual Technical Conference and Exhibition held in Houston, Texas, 3–6 October 1999.

Field trials and physical modeling of wells with downhole water sink (DWS) completions have demonstrated controlled water coning and increased oil production rate. However, no field trials were long enough to show DWS potential in improving of oil recovery in comparison with conventional wells. Presented here are theoretical and experimental results from a DWS recovery performance study. The recovery study involved experiments with a physical model and computer simulations. The experimental results reveal that DWS dramatically accelerates the recovery process; a fivefold increase of the oil production rate was reached by adjusting the water drainage rate at the bottom completion. The results also show a 70% increase of oil recovery; from 0.52 to 0.88 for conventional and DWS completions, respectively. The computer-simulated experiments with commercial reservoir simulator demonstrate progressive improvement of recovery with downhole water drainage from 0.61 to 0.79 with no drainage and maximum drainage, respectively—a 24% increase of recovery factor, and a fivefold reduction of the time required to reach the limiting value of water cut, 0.98. However, the accelerated recovery process with DWS requires a substantial, up to 3.5-fold, increase of total water production. The simulation experiments also show that the main advantage of using DWS is its flexibility in controlling the recovery process. For conventional completions, recovery could be slightly increased by reducing production rates and largely increasing production times. For DWS, a combination of the top and bottom rates could be optimized for maximum recovery and minimum production time.