Successful Field Trials of Water Control in High Water Cut Wells Using an Improved Downhole Water Sink/Drainage System

Abstract

Abstract The K1h23 and K1h27 at Luliang Oilfield Block 9, are thin-layer bottom water drive reservoirs. Traditional water control techniques including partial perforation, injection chemicals to form an artificial barrier, have been implemented at early on to delay the water breakthrough. However, after years of production, the water coning is fully established in many production wells. Those traditional water control techniques did little success to control the water cut after water breakthrough. Effective water control technique for high water cut wells is needed to prevent premature well abandonment. Downhole Water Sink/Drainage technology is a dual completion method with in-situ simultaneous production of oil and water. With proper design, the hydrodynamic balance at WOC can be obtained to suppress the water coning, therefore, reducing water cut in high water cut wells. Whereas, the nature of those high water cut wells in K1h23 and K1h27 reservoirs makes it difficult to use the currently available Downhole Water Sink /Drainage system which would require dual tubing string production or single tubing string with tubing/casing annulus flow path. Since those high water cut wells in K1h23 and K1h27 reservoirs are usually old wells cased with 5.5 in tubular, making it unsuitable to accommodate two parallel tubing string. The severe paraffin and corrosion problem in the wellbore further preclude the option of producing fluids through tubing/casing annulus flow path. Because of that, an improved Downhole Water Sink/ Drainage system is developed to overcome the above challenges. The improved Downhole Water Sink/Drainage system is a single tubing string completion system. The improvement of this system is the use of the hollow rod as a sucker rod for sucker rod pump to produce the lower water zone through the hollow sucker rod while producing upper oil zone through tubing string. Separate artificial lift for both oil and water production can be achieved. The system utilize the existing well condition in which sucker rod pump has already been used as a means of artificial lift in high water cut wells, result in high operation efficiency and low operation cost. The field results of two pilot wells show that the implementation of this system enable the water cut in the upper oil completion to reduce from over 80% to less than 50% and the oil rate increase up to several fold. Field data of the production history, reservoir performance, and well configuration of this system are presented with discussions. The successful field trials of this two pilot wells prove the effectiveness of this improved Downhole Water Sink/Drainage for water control in high water cut wells with challenging conditions. For other mature fields with similar or better reservoir and well condition, this water control system can also be applied with little modifications.