Application of Downhole Oil-Water Separation: A Feasibility Study

Abstract

Abstract An engineering feasibility study has been conducted on the major operated oil field of waha oil company to determine the feasibility of applying downhole oil/water separation technology (DHOWS) and to rank candidate wells within this field on the basis of their suitability for a DHOWS instalilations. Under operations consistent with the existing field development (or any future developments), the nature of the GE reservoir is such that, the remaining oil reserves will have to be produced at high and constantly increasing watercuts. Downhole separation and disposal of produced water represents a material opportunity to improve the current and future operations of the field. A screening template was developed to review the reservoir and well characteristics in more details and to identify a list of candidate wells for the possible implementation of DHOWS technology. Several operational risk and concerns exists in respect of the candidate wells were identified. Eighteen wells our of twenty four wells demonstrated favourable reservoir and well characteristics and meet the initial DHOWS screening criteria. The screening template may be used to evaluate other fields for potential conventional DHOWS applications. A preliminary design of a DHOWS application for three wells is presented in this paper. Introduction It is widely known that the continouse increase in the amount of water production hinder the oil production rate, contributes to high operation expense and is a major source of environmental concern to the oil companies. In the past, the response of operators to increasing water poroduction rates was to production to the top section of the oil well away from the rising water, while trying to slow the advance of water with sequeze cement and cement plug techniques. The oil industry experiences with these techniques have shown mixed results. Meanwhile, if water cannot be stopped and the cost of handling the water in additional to other costs exceed the revenue, the operator has to abandon the well despite the fact that significant volume of oil are still being produced. The Center for Engineering Research Inc. initiated a feasibility study in 1991 to test a new technique to reduce water-handling costs by reducing the volume of water produced at the surface. This work produced the idea of combining separation and pumping systems downhole and simultanouse injection of the produced water in the same wellbore. Mattews et al.1 presented a novel system for downhole separation and same well reinjection of produced water. The technique was applied to two wells in the Alliance Field and the results indicated an increase in oil rates. Peachey et al.2 presented a brief summary of field trails completed and the key results achieved, including oil production increases, water reduction, predicted increases in reserves recovery and general factore affecting the a successful DHOWS application. Shaw et al.3 indicated that The DHOWS technology could be applied successfully in a low risk wells. They defined risk as a fuction of workover cost and deferred production; high risk therefore being a prolific well with high workover costs. Scaramuzza et al.4 described the seperation system implemented in Grey, Red and Green sands of Barrancas formation, the candidate wells selected, the results of pilot field trails. Li et al.5 conducted indoors dynamic simulation experiments to test downhole separation and injection technique for rod pumping well. Jokhio et al.6 reviewed in some detail the economic parameters that effects DOWS and summarized the characteristics of a waterflood operation that can benefit economically from this technology. The aime of this feasibility study is to determine the technical and economic feasibility to use the downhole oil/water separation system in GE reservoir, to rank candidate wells within this field on the basis of their suitability for a DHOWS instalilations, and to develop a screening template that can vbe used in evaluation of oil fields for potantial DHOWS applications. Reservoir Characteristics The suitability of the GE reservoir, for DHOWS applications, was examined in respect of the observed/demonstrated reservoir behaviour. GE reservoir has been under primary recovery operations since 1964. The succeeding sections individually examine each of the following reservoir characteristics: reservoir geology, drive mechanism, production history, and water disposal/injection zone potential.