Abstract: A pumping apparatus is disclosed which uses a reversible, variable displacement hydraulic drive pump capable of pumping fluid under pressure. A hydraulic cylinder enclosing a piston is operatively connected to a port of the hydraulic drive pump. A fluid accumulator, which is precharged to a selected precharge pressure, is operatively connected to the other port of the hydraulic drive pump. The fluid accumulator supplies the fluid under the precharge pressure to the hydraulic drive pump. The hydraulic drive pump increases the pressure on the fluid to a working pressure required to drive the piston from a first position in a first direction to a second predetermined position. Upon reaching the second position, the hydraulic drive pump reverses direction to reverse the flow of fluid from the hydraulic cylinder thereby reciprocating the piston back to its first position, and directing the fluid to the fluid accumulator.

Abstract: A pumping apparatus includes a reversible variable displacement drive pump having two ports and a lifting apparatus connected to one of the ports. The lifting apparatus is designed to fit on the well-head of an oil well and attach to the polish rod of the well to operate a down-hole pump. A fluid accumulator containing a precharge is connected to the second port of the drive pump. A pump-off control system automatically adjusts the pumping rate of the lifting apparatus to the individual rate of formation flow of a particular well.