The application of downhole gas water separation (DGWS) technology, which offers both economical and environmental benefits, was restricted by the complicated system designing and rigorous requirements for candidate wells. This paper provided a hydraulic system designing method for the ESP/DGWS system to determine the parameters of the downhole separator and the electric submersible pump. The structure and principle of system was introduced firstly, and then the whole system was divided into five subsystems: the production zone, the downhole separator, the ESP system, the disposal zone and the pipe flow system. The flow behavior in each subsystem was studied separately and a hydraulic designing system method was establish using the nodes analysis method to determine the separator type, the ESP type, the depth of separator, the stages of pump and other relative parameters. A computation procedure of this method was presented to provide a practical way for the application of the method in gas field and an example was included to illustrate the procedure.
Produced water is the largest volume of waste stream associated with oil and gas production. In today's operations, water is generally pumped to the surface along with gas, and then separated on the surface. The lifting, treating and reinjecting of the produced water cost a lot and the accumulation of water in the well bore may even kill a gas well and the recovery is reduced greatly.
The downhole gas water separation (DGWS) represents a novel solution to the significant environment and cost issue for gas operators, which separate the gas and water downhole and reinject the produced water in the same well. DGWS came into industry in the early 1990s and has received a great deal of attention during the past decade and many fields tests were done in the late 1990s. There are mainly four types of DGWS in the industry: bypass tools, modified plunger rod pumps, electric submersible pumps (ESP) and progressive cavity pumps (PCP). The treatment capacity and the recommend install depth of each type are shown in Table 1[1].
Although the ESP/DGWS handles much higher flow rates and easy to be operated, only a few ESP/DGWS systems have been installed in the field compared to other type of DGWS. Since the ESP/DGWS system is quit complicated compare to the ordinary lifting or injecting system, more research is still required to improve the reliability and the stability of this novel technology. Two major aspects associated with the applications of ESP/DGWS are the structure of the downhole tools ("hardware") and the hydraulic designing ("software") of the whole system. The aim of this paper is to analysis the system composition of ESP/DGWS system and to provide a practical hydraulic designing method for the system.
The ESP/DGWS system comprises a downhole separator combined with an electric submersible pump. The produced fluid (gas and water) goes into the separator first where the lighter phase and the heavier phase are separated due to the gravity and centrifugal force, and the light phase goes up to the well head while the treated water flow downward into the ESP.
