| 摘要 |
A downhole pump for a well is disclosed which includes a piston slidably disposed within a housing for pumping fluid from the well. The longitudinal axes of the piston and the housing extend in a generally vertical direction with respect to the surface of the well. A surface unit supplies a pulsating flow of fluid to the piston. A velocity actuated valve is formed in the piston and includes a ball which is spaced from an orifice by a bias. The bias holds the ball away from the orifice such that the valve is normally open. The flow of fluid through the velocity actuated valve during each fluid pulse creates a pressure differential which is resisted by the bias. When the pressure differential exceeds the force generated by the bias, the ball will seat in the orifice and close the valve to further fluid flow. The balance of the fluid pulse will be applied to the lower side of the piston and the piston moves upwardly within the housing, thereby pumping fluid from the well. At the end of each fluid pulse, the pressure will drop such that the bias forces the ball away from the orifice. Thus, the velocity actuated valve is opened and fluid can flow freely therethrough, to permit gravity to move the piston downwardly for the next power stroke and permits production fluid to enter the housing through a traveling valve and bottom discharge valve and flow through the velocity actuated valve to the upper side of the piston.
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