An Analytical Model for Water Coning Control Installation in Reservoir With Bottomwater

Abstract

Summary Water coning is a serious problem in maturing reservoirs with bottomwater drive where depleted oil strata overlays sizable water zones. The resulting high values of water cut and minimal oil rate lead to early shutdowns of the wells without sufficient recovery of hydrocarbons in place. For many years, reservoir engineers have looked for effective ways to control water coning, but only a few successful oilfield examples have been reported. Usually, in the presence of bottomwater, wells are completed in the upper section of the pay zone and produce oil below the critical rate in order to prevent or delay water coning. Typically, however, the critical rate is too low to be economical so that high water cut becomes inevitable. Downhole water sink (DWS) technology, a relatively new and effective method to control water coning, has been increasingly considered by engineers worldwide. Theoretical calculations and field practice have shown that DWS can improve oil production rate, reduce water cut and increase the oil productivity index of a well. However, the technique requires draining and lifting large amounts of water from the aquifer, which increases the cost of production. In order to solve the DWS water lifting problem, a new water coning control method called downhole water loop (DWL) installation has been developed. It has the same advantages as the DWS technique, but it does not need to lift water to the surface. This paper addresses the feasibility of DWL installation and analytically examines the mechanism of producing water-free oil from the DWL of bottomwater drive reservoirs. The DWL feasibility is tested with a simple analytical model derived in this study. Also, a good match is obtained when comparing the model-calculated data to real production data.