| 摘要 |
A downhole, electro-hydraulic pump assembly, having a hydraulic power piston connected to a double-acting production piston is disclosed. Hydraulic power for operating the power piston is developed downhole by a mechanical pump which is driven by an electrical motor carried within the pump housing. The electrical motor is energized by high-cycle electrical power conducted from a surface facility for increased pumping capability in very deep wells. Long stroke capability is provided by an annular piston and a tubular connecting ram which ride on a tensioned guide tube. The effective production piston area is maximized for efficient production in both up-stroke and down-stroke by conducting the flow of formation fluid produced in the down-stroke through the bore of the tensioned guide tube. The electric drive motor and hydraulic drive pump are operated safely at high power levels because of the improved heat dissipation arrangement in which the electrical motor and pump are cooled by circulation of the power fluid within the pump housing, with the power fluid being continuously circulated to the surface through a filter and heat exchanger. In a preferred embodiment, the downhole electrical drive motor is energized from the surface by a cyclo-converter having a continuously variable frequency output, whereby the stroke speed is also continuously variable over a wide range to accomodate changes in the producing formation.
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