Abstract: A method and apparatus for pumping water, oil, or other production fluid up a production tube from a well or the like to achieve greater efficiency as compared to conventional pumpjacks. A hydraulic actuator unit with its own hydraulic fluid incorporates pressure sensing valves to move a hydraulic piston through a power stroke and a resetting stroke. A power transmission tube having its own power fluid transfers pressure from the hydraulic actuator to a downhole piston assembly to pump the production fluid directly up the production tube during a power stroke. The static head of the production fluid in the production tube resets the downhole piston assembly during the resetting stroke. The pressure sensing valves enable the hydraulic piston to extend its power stroke a sufficient distance to pressurize the power transmission fluid and move the downhole piston assembly through its entire production stroke independent of the compressibility of the power transmission fluid.

Abstract: A pumping apparatus (10) is disclosed which includes a downhole reservoir unit (20), a pumping unit (18) and a power unit (102). The reservoir unit (20) has a piston assembly (70) with a top piston (72) and a bottom piston (74). A storage chamber (82) is defined between the two pistons (72, 74) which is variable in volume as the piston assembly moves from the rest position to a pumping position where a helical spring (98) is compressed. The piston assembly (70) is moved by fluid in a tubing string (22) through reciprocal motion of a pulser piston (48). As the piston assembly (70) is moved downwardly, fluid from the reservoir passes through a check valve into the storage chamber (82). When the piston assembly (70) is in the pumping position, the pulser piston (48) is retracted and the helical spring (98) drives the piston assembly (70) upward. The volume of the storage chamber (82) decreases and fluid is pumped from the storage chamber through the tubing string to the surface.