Patent ID: 8302677
Filing Date: 2012-11-06
Classification: E21B,F16D

Abstract:
1. A control circuit for a coiled tubing injector for raising or lowering coiled tubing into a well, the injector including an injector motor to power an injector drive mechanism, the injector drive mechanism engaging the coiled tubing to raise or lower the coiled tubing, the circuit comprising: a circuit controller for varying power to the injector motor to maintain a substantially constant weight on bit; and the circuit controller controlling the injector motor to exert a controlled upward force on the coiled tubing less the coiled tubing string weight, thereby resulting in a substantially constant weight on bit, said circuit controller comprising a hydraulic circuit controller, which reacts to a hydraulic pressure to maintain a substantially constant weight on bit; a counterbalance valve opening in response to the circuit controller to power the injector motor for rate of penetration movement of the coiled tubing and closing in response to the circuit controller to prevent the tubing string from descending into the wellbore; a bypass line around the counterbalance valve; and a control valve for opening to bypass the counterbalance valve.