Field Study: Utilizing a Progressing Cavity Pump for a Closed-Loop Downhole Injection System

Abstract

SPE Members Abstract The information contained in this paper is based upon the field test of an experimental closed-loop injection system. The basis of the test was to determine both functionality and future feasibility. The system was installed in an existing water flood where the water source zone and the injection zones were completed in the same wellbore. The two zones were isolated by a bottom packer and a second upper packer, installed above the water source zone, which allowed the casing to be pressure tested to meet state regulatory requirements. The pumping system consisted of a sucker rod driven progressing cavity (PC) pump installed below the bottom packer. The sucker rods and pump rotor were driven from the surface by a variable speed hydraulic drive system. Water from the water source zone entered the pump through a perforated sub in the tubing string above the pump and was pumped into the injection zone. Downhole pressure gauges were initially installed to determine the differential pressure across the pump. A downhole flow meter was later installed to determine actual flow rates into the injection zone. Introduction The concept of a downhole progressing cavity (PC) injection pump was originally developed for dewatering gas wells. The conventional method of operation is to produce the water and gas to the surface via the tubing and casing, then transport the produced water to a disposal well and inject it into a disposal zone. In Michigan, in production from the Antrim, gravity disposal is widely utilized. The well is completed through the disposal zone below the water and gas producing zone. The water and gas enter the wellbore and the water falls to the disposal zone due to the hydrostatic head; the gas is produced up the annulus to the surface. This method of production works fine until the disposal zone pressures up, then a pump must be used to overcome the increased pressure. The PC pump is widely utilized in this area to produce the water to the surface, therefore, due also to its simplistic operation, the pump was considered in the design of the downhole injection system. Due to slow response from regulatory bodies in approving the PC pump method of production and disposal, the concept was targeted for usage in other areas of production. Water flooding, being widely utilized throughout the oil field, became the focus for the application of this concept. The strict environmental regulations and the liabilities associated with the transportation of produced fluids has generated due concern for operating companies. An injection system such as the closed loop PC pump injection system would reduce the risk of exposure to environmental regulations and accidents by eliminating the need for large water storage and pumping facilities as well as extensive, leak prone flow line systems. This system would also reduce corrosion problems associated with conventional injection systems. The progressing cavity pump was easily adapted to this application. The continuous positive displacement without the use of valves enables the PC pump to inject at a constant rate. P. 301^