Abstract: A Hydraulic Pumping Unit equipped with a flywheel, a high-slip electric motor and a reversible hydraulic pump such that during the downstroke of the Unit, the hydraulic pump operates as a hydraulic motor, accelerating the flywheel and accumulating in this way the energy of the downgoing rodstring in the form of kinetic energy.The interaction between the flywheel, electric motor and weight of the rodstring adjusts automatically the range of speed variation.The upward and downward speeds of the Hydraulic Pumping Unit can be adjusted by hand or automatically by electronically commanded step motors, in such a way that the Hydraulic Pumping Units adjusts itself to the varying conditions of the oilwell.