A variable displacement pump-motor includes a pump-motor having a plurality of cylinders and pistons, and further including a main shaft rotatable relative to the system body. A hydro mechanical control system includes a plurality of main stage valves in communication with the plurality of cylinders. Each of the main stage valves is configured to open and close a cylinder of the plurality of cylinders to one or more of high or low pressure fluid sources. A pilot spool valve is in selective communication with each of the main stage valves. The pilot spool rotates with the main shaft. The pilot spool includes coding configured to operate each of the main stage valves to open and close the respective cylinders to the one or more high and low pressure fluid sources according to a translational position of the pilot spool and rotation of the pilot spool by the main shaft.

A hydraulic system is provided for powering one or more external hydraulically powered devices. The system includes one or more pumping systems attached to a common crankshaft and including an inner sleeve, an outer sleeve, a valve member and an end body. The system can include a pair of high pressure fluid tanks and a low pressure fluid tank. The pumping systems can increase the fluid pressure within the high pressure fluid tanks back and forth and in a sequenced manner, and force the higher pressure fluid through the one or more powered devices. Drive systems are provided to assist the pumping systems in rotating the common crankshaft. The drive systems can include a piston assembly for rotating the crankshaft and a valving system for directing fluid into the piston assembly to power the piston assembly.

Methods and systems for a mechanically driven pump are provided. The mechanically driven pump may apply a piston simultaneously to operate as a guillotine blocking valve and a component to transfer motive force. A spring may apply a force to the piston to oppose a force that is applied to the piston via a cam lobe. The mechanically driven pump exhibits a differential pressure at a calibrated orifice during two working phases of the pump (expansion and compression), which provides for a non-zero volumetric efficiency of the mechanically driven pump.

Method and apparatus overcoming gas-lock in reciprocating downhole pumps. On the downstroke of a plunger in a barrel, gassy fluid is compressed in the pump chamber between standing and travelling valves. Downhole plunger movement drags a sleeve over a mandrel for opening a chamber valve to a staging chamber located at a downhole end of the travelling valve for receiving at least a portion of the compressed and gassy fluid therein. On the upstroke, the chamber valve is dragged closed for sealably retaining the compressed gassy fluid therein while drawing an additional increment of fluid through the standing valve into the pump chamber. Continued downstroke and upstroke cycles increases pressure of the compressed gassy fluid in the pump chamber until it exceeds the hydrostatic head above the travelling valve for resumption of normal fluid pumping.

A variable displacement pump-motor includes a pump-motor having a plurality of cylinders and pistons, and further including a main shaft rotatable relative to the system body. A hydro mechanical control system includes a plurality of main stage valves in communication with the plurality of cylinders. Each of the main stage valves is configured to open and close a cylinder of the plurality of cylinders to one or more of high or low pressure fluid sources. A pilot spool valve is in selective communication with each of the main stage valves. The pilot spool rotates with the main shaft. The pilot spool includes coding configured to operate each of the main stage valves to open and close the respective cylinders to the one or more high and low pressure fluid sources according to a translational position of the pilot spool and rotation of the pilot spool by the main shaft.

Methods and systems for a mechanically driven pump are provided. The mechanically driven pump may apply a piston simultaneously to operate as a guillotine blocking valve and a component to transfer motive force. A spring may apply a force to the piston to oppose a force that is applied to the piston via a cam lobe. The mechanically driven pump exhibits a differential pressure at a calibrated orifice during two working phases of the pump (expansion and compression), which provides for a non-zero volumetric efficiency of the mechanically driven pump.