Artificial lift system for oil wells

Abstract

Oil is recovered from underground formations more efficiently by the use of a subsurface power piston that reciprocates a subsurface pump. A series of connecting rods called sucker rods connects the power piston to the subsurface pump. The subsurface power piston is driven upward by a surface mounted hydraulic actuation system. The power piston and sucker rod travel downward by the force of gravity. The distance between the subsurface pump and power piston is set so the pressure at the depths of the power piston and pump closely counterbalance the weight of the sucker rod string at all positions of stroke with a slight down bias. The free-body piston of the surface actuator acts as a membrane member between the refined oil of the surface actuation system and the fluid being recovered. The pumping action occurs on the downstroke of the subsurface equipment. The pumping speed is automatically and optimally adjusted according to fluid parameters. The upstroke speed can be different from the downstroke speed for increased production. The time between the pressure pulses to the power piston is easily adjusted to reduce sucker rod oscillation and stresses, and to control the time between pump cycles.