Method and system for energy recovery from a rod pump

摘要

A system includes, in an exemplary embodiment, a hydraulic cylinder having a barrel, a piston connected to a rod string of the rod pump, and a pressure chamber; a reversible hydraulic pump connected to the pressure chamber; and a motor-generator having a rotor shaft connected to a coupling shaft of the pump. The motor-generator operates in a motor mode to rotate the rotor and coupling shafts in a forward direction so that the hydraulic pump pumps hydraulic fluid to the pressure chamber to raise the piston and rod string in an upstroke, and operates in a generator mode in which a weight of the rod string displaces the piston in a downstroke to pump hydraulic fluid from the pressure chamber to rotate the pump coupling shaft and the rotor shaft in a reverse direction such that the motor-generator generates electricity. A variable speed drive modulates the speed of the motor-generator.