METHOD AND APPARATUS FOR ACTUATING A SUB-SURFACE RECIPROCAL WELL PUMP

摘要

A subsurface well pump actuator drive having a pair of slave cylinders and a pair of auxiliary control cylinders mounted on a wellhead and connected to a pumping string of rods for reciprocal pumping movement of a given stroke. A closed accumulator is connected to the slave cylinders and pressurized to such an extent as to liftingly position the string of rods at a balance point in the middle of the pump stroke with automatic valving means supplying hydraulic pressure to the control cylinders to cause upward movement from the midway balance point to the top of the stroke and for supplying hydraulic pressure upon reaching the top of the stroke to cause reverse movement to the bottom of the stroke after reaching the midpoint balance with the slave cylinders providing the majority of work for the upward stroke.