Application of Downhole Oil/Water Separation Systems in the Alliance Field (1996)

There is growing recognition and concern for the adverse impacts that ever increasing volumes of produced water have on oil production operations and reserves recovery. New technologies must be developed and successfully implemented to minimize the negative economic and environmental consequences of water production. Taking a novel approach in addressing these concerns, the Centre For Engineering Research Inc. has developed systems for downhole separation and same well injection of produced water. These systems have demonstrated significant potential to alleviate the high costs, production limitations and environmental risk associated with the handling of large volumes of produced water at surface.PanCanadian Petroleum Ltd. has deployed several of these systems in field trials at its Alliance operation in Canada which produces 38 API oil from a sandstone reservoir. The paper describes the candidate wells selected and the separation systems used in this application. Issues related to well conversions and system installation are reviewed and preliminary results from the field trials are presented.IntroductionProduced water contributes to high operating expenses and is a major source of environmental concern for oil producers. Excessive water production also results in many wells and fields being suspended and abandoned, despite the fact that significant volumes of oil are still being produced. While it is not often reported, the water volumes produced in association with conventional oil are significant. In Canada, the oil industry produces almost six cubic meters of water, on average, for every cubic meter of oil produced. Some wells can be produced economically with water to oil ratios of over 100 with conventional production methods, but most wells currently become uneconomic at ratios as low as 10:1 or 20:1 due to the lifting and water handling costs.The Centre for Engineering Research Inc. (C-FER) initiated a feasibility study in 1991 to examine non-conventional means to reduce oil well lifting and water handling costs by reducing the volume of water produced to surface. This work resulted in the idea of combining hydrocyclone separators with conventional downhole oil field pumping systems to accomplish oil production, oil/water separation and simultaneous injection of the produced water in the same wellbore An ongoing joint industry project was subsequently organized by C-FER to further evaluate this concept through the development and testing of prototype separator systems. The project scope includes the development and field testing of prototype equipment for three downhole separation systems based on electric submersible pump (ESP), progressing cavity pump (PCP) and beam pump lift systems. The main objectives of the field tests are to demonstrate the operation and prove the economic benefits of the respective separation systems. The research and development project also addresses economic feasibility modeling, well recompletion design strategies and reservoir modeling to assess implementation of the technology in different fields.The many potential benefits associated with downhole oil/water separation and same well injection of produced water have been described previously by Peachey, 1991. This paper provides a description of this novel technology and presents the results from some of the initial field trials undertaken by PanCanadian Petroleum Ltd. with ESP oil/water separation systems.Downhole Separation SystemsThe downhole oil/water separation (AQWANOTM) systems under development by C-FER consist of a hydrocyclone separator coupled to a modified conventional pumping system. The hydrocyclone separator units employ standard liquid/liquid hydrocyclone liners (Colman, 1980, Schubert, 1992) which have been packaged for downhole service.P. 453