The Development Of Bottom Discharge Submersible Pumps

Abstract

Abstract Abu Dhabi Company for Onshore Oil Operations (ADCO) employs water injection for pressure maintenance in its three major oil-producing fields. An auto-dump injection scheme is used to naturally inject water from overlying aquifers into the reservoir due to the differential pressure. A paired water supply/injection well system is also used, by which the water is lifted to surface by Reda electric submersible pumps and injected by surface pumps driven by electric motors. ADCO has tested a unique approach to boost the dump flood in the field. A bottom-discharge submersible pump has been designed to increase the water available from the aquifer for dump flooding, providing a combination of both dump and power injection. The approach offers the advantage of reduced power requirements and eliminates the need for a water supply well and surface injection equipment. Also it utilises the natural dump when a pump fails. A proto type M 675 (26-stage) bottom discharge submersible pump was ordered from Reda and was first tested in February 1975. This pump, powered by a 500 HP motor developed a pressure boost of 1000 psi and increased the natural dump of 5000 bw/d to a powered injection rate of 15,000 bw/d. Selection of pump size with the appropriate number of stages showed that most well requirements could be met by J-600 or J-400 bottom discharge pumps which can be set inside 9.5/8 inch casing. In order to carry out more tests a 55-stage J-600 submersible bottom discharge pump was installed in well Bu-114. Many changes in the design of the downhole equipment were carried out to simplify running and improve reliability and, although further improvements may be necessary, it is clear that the bottom-discharge concept of injection is a highly viable and economic proposition where surface water is not available or at a premium for other uses. Introduction Abu Dhabi Company for Onshore Oil Operations (ADCO) is currently injecting some 1,600,000 barrels of water per day for reservoir pressure maintenance in the three main producing fields. Powered injection is by means of a paired water supply/injection well system, with water lifted by 18 stage N-1050 Reda pump powered by a 500 HP motor (fig. 1). The water is injected into the reservoir using surface pumps up to a pressure of 2400 psi. The typical installation of a Reda N-1050 submersible pump is shown in fig. 2. The pump has an operating range from 22,000–35,000 bw/d. ADCO is expanding its water injection capability by equipping some existing dump injection wells with bottom-discharge submersible pumps. They offer the following advantages over the conventional "up and over" paired injection/water supply well configuration:–Very low capital investment, in respect of power generation, overhead transmission lines, surface pumping equipment and elimination of a separate water supply well.–A higher overall operating factor since many wells will continue to dump if a pump fails.