Surface power unit for a downhole pump

Abstract

A surface power unit for use on a subterranean well generates a series of pulses of pressurized fluid to a downhole pump. A pump means generates a flow of fluid from a reservoir through a charging line to a charging side of a cylinder. A piston is slidably disposed within the cylinder, dividing the cylinder into the charging side and a power side. Position or pressure transducer means responsive to the movement of the piston generates control signals representing the position of the piston in the cylinder. The charging line can include a first valve means responsive to one of the control signals for regulating the flow of fluid through the charging line. A return line is provided for returning fluid from the charging side of the cylinder to the pump means. The return line includes a second valve means responsive to another one of the control signals for regulating the flow of fluid through the return line. Whenever the first valve means is closed to permit fluid to flow through the charging line into the charging side of the cylinder, the second valve means is opened to prevent fluid from escaping from the charging side of the cylinder and the piston is moved through a power stroke to generate a pressurized fluid pulse, then the first valve means is opened, and the second valve means is closed. A return pipe supplies fluid from the well to the power side of the cylinder to move the piston through a return stroke. A power line supplies the pulses of fluid generated by the movement of the piston in the cylinder to the downhole pump. In alternate embodiments, an energy storage tank is connected between the well and the return pipe; the first and second valve means can be a four-way valve; or the first valve means can be eliminated.