Abstract: An electric submersible pumping system includes a motor comprising an inner hollow core rotor and an outer stator, a gearbox comprising a hollow core input shaft connected to the motor rotor, and a hollow core output shaft, and a pump driven by the gearbox output shaft, the pump having an intake, and wherein the pump output is directed through the hollow core output shaft and into the hollow core motor rotor. The motor section is disposed above the gearbox and pump.

Abstract: A jar tool for use in a drill string for use in dislodging a drill bit or well-tools trapped in well bores. The tool comprises an outer housing adapted to move longitudinally with respect to an inner spline mandrell. A piston assembly is acted on by a piston actuator and hydraulic fluid restricts the movement of the piston assembly and, therefore, the movement of the mandrell relative to the housing, while the piston assembly is within a narrower portion of a hydraulic cylinder. When the piston assembly reaches a larger diameter portion of the cylinder, the hydraulic fluid rushes past the piston assembly which allows a knocker connected to the spline mandrell to collide with the outer housing. A compression spring returns the piston assembly to its rest position abutting a shoulder on the outer housing. Provision is made for pressure release values to be inserted in the piston assembly so that the tool can be operated within minimum and maximum operating limits.