| 摘要 |
A positive displacement pump for pumping fluids from a downhole formation to the earth's surface is provided. The pump (100) first comprises a plunger (130). The plunger is reciprocated axially within the wellbore by a linear actuator (300), such as a submersible electrical pump, in order to form an upstroke and a downstroke. A pump inlet (140) is disposed near the bottom end of the plunger, while a pump outlet (150) is disposed near the top end of the plunger. The pump is configured such that it is able to pump a first volume of fluid upward within the wellbore during the pump's upstroke, and a second volume of fluid upward within the wellbore during the pump's downstroke. Thus, the pump is "double-acting", that is, it is able to displace fluids both on the downstroke and on the upstroke. The pump also permits the capture of a greater volume of fluids without a corresponding increase in velocity of the fluids through the pump. Furthermore, the pump is substantially hydrostatically balanced.
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