Multi-Cylinder Hydraulically-Driven Pump System

A hydraulically-driven pumping unit for pumping a working fluid, the pumping unit comprising:

• a first double-acting hydraulic piston-cylinder (HPC) assembly comprising a first central axis, a first hydraulic cylinder, a first piston, and a first rod coupled to the first piston for axial movement relative to the first hydraulic cylinder;
• a second double-acting hydraulic piston-cylinder (HPC) assembly comprising a second central axis, a second hydraulic cylinder, a second piston, and a second rod coupled to the second piston for axial movement relative to the second hydraulic cylinder;
• a hydraulic fluid source;
• and
• an exhaust path for hydraulic fluid;
• wherein the first and second hydraulic cylinders are coupled to the hydraulic fluid source and the exhaust path such that movements of the first and second pistons are synchronized;
• wherein the first and second HPC assemblies are configured for phase-shifted operation such that when pumping unit is reciprocating the two pistons and rods, the second piston and rod always have a different combination of axial position and direction of travel than do the first piston and rod, and such that at least one of the two rods is moving to extend further beyond the corresponding hydraulic cylinder at all times.