There are limitations to the amount of free gas that can be handled by high volume downhole pump systems. A new pump design employing axial flow impellers coupled with high speed downhole turbine drive has been developed, and is the first true downhole multiphase pump. This paper describes the staged research and development program leading to the first field trial installation in the Captain Field, in the North Sea. Development and design requirements are reviewed, with the results from laboratory testing in water and nitrogen followed by full scale loop testing in multiphase fluid, including crude, methane and brine. Test configuration is described, and key performance results reviewed. Special testing defined the nature of fluids and rheology related to high rotational speed pumping of viscous crude and brine mixtures in pumps and pipelines. Following successful laboratory scale testing, design considerations are reviewed for its application in a field trial. Completion design includes provision for open loop flow and access below the pump assembly for coiled tubing intervention. New downhole monitoring systems employ pump and turbine monitors along with pump flow and reservoir evaluation monitoring. The design results in extended range of pump operability, improved reliability, and improved control and reservoir management. Introduction As technology improves in horizontal drilling, completion practices, and subsea equipment, the need for high volume downhole pumping systems has increased. Small accumulations or thin oil zones, previously considered marginal, can be exploited economically. But in some applications, pumping systems needed higher gas handling capability because maximizing recovery from individual wells requires larger pressure drawdown. Additionally, horizontal wells located at the top of the productive intervals can encounter free gas caps. Development of a downhole pumping system that could operate successfully in a gassy environment (higher than 30% gas void fraction), and deliver high reliability was key to exploiting new reserves. This technology could be applied within many major oil compani's existing asset portfolio, such as the Gulf of Mexico or West of Shetlands deepwater environments, and elsewhere in the North Sea. One of the assets that could benefit from this technology is the Captain Field. Although the main area of the field is being developed with Electrical Submersible Pumps (ESP), an isolated gas cap was identified in the eastern section of the field that would limit the reliability of ESP systems, and would limit the withdrawal rate. The field has 19 degree API crude oil, with 88 centipoise (CP) viscosity at reservoir pressure of 1300 psi and 87 deg F.
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