| 摘要 |
A combined surface power unit and velocity actuated valve for a downhole pump is disclosed. The surface power unit generates a series of pulses of pressurized fluid. A power line supplies the fluid pulses to a downhole pump. Within the downhole pump, a piston means is slidably disposed for pumping fluid therefrom. The piston means includes an orifice for permitting fluid flow therethrough. The velocity of the fluid passing through the orifice causes a pressure differential across the orifice and valve means closes for the duration of each pulse. When the valve means is closed, pressure builds up in the downhole pump causing the piston means to move in a power stroke, pumping the production fluid. Between pulses, the pressure of the fluid in the downhole pump drops and a velocity valve opens. When the velocity valve is opened, fluid can flow freely therethrough, and the piston means retracts under the influence of gravity in a re-charging stroke.
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