New-Type Energy-Recovering Hydraulic Workover Rig and the Simulation for Lifting the Tubing String

A new-type energy-recovering hydraulic workover rig is researched. The basic structure and working theory of this rig are introduced. This rig decreases its equipped power remarkably compared with the conventional rig, and can recover the potential energy released by the tubing string when lowered. With infinite force-grade number, this rig can obtain the maximum lifting efficiency and energy-recovering rate. The dynamics model of lifting the tubing string is deduced and a simulation analysis is conducted. Through simulation some conclusions are obtained: (1) the greater the throttle valve path area the higher the tubing string lifting velocity, (2) the lighter the tubing string the higher the tubing string lifting velocity, and (3) the greater the displacement of the variable pump motor the higher the tubing string lifting velocity. The actual measurement results prove that the dynamics model and simulation results are basically right.