Research On Technique Of Pipe Free For Workover Rig

Illustrated the working principle, advantages and disadvantages of pipe free devices with different structures through analyzing the application situation of technique and equipment for pipe free at home and abroad. In view of functional requirement for pipe free device in workover treatment, and in order to realize safety and high efficiency in pipe free, we developed a device used to assist workover rig lifting tubing string from the well in workover treatment, the device adopts remote hydraulic control, which is safe and reliable.The pipe free device is mainly made up of hydraulic lifting unit, hydraulic slip unit, hydraulic supporting unit, hydraulic power system and hydraulic control system. Hydraulic lifting unit is the main driving component in pipe free, it is used to lift stuck tubing strings. Hydraulic slip units are mainly used to bear load, they can be used as fixed hydraulic slip and traveling hydraulic slip. They can clamp tubing string at arbitrary position reliably when the device works. Hydraulic lifting unit can lift stuck tubing string coordinates with hydraulic slip unit. The bases of hydraulic supporting unit can be controlled to adjust supporting height, which make the hydraulic supporting unit can share the large load when lifting tubing string to prevent casing in well from failure. The hydraulic power station is arranged rationally, and its physical model is built by computer. All the hydraulic pressure cells are fixed on a base unit by advisable design, so the hydraulic power station can be moved conveniently.Hydraulic slip units are mainly used to bear load, whether the pipe free device can works in security lies on the intensity of slip shells and slip teeth. We designed the hydraulic slip units according as the demand of pipe free, and compute the slips and slip teeth with finite element method by SolidWorks and ANSYS to verify security of the device.On the base of theory research, we did some indoor and field experiments. We tested performance of the pipe free device and got some parameters such as the device's lifting force under the corresponding working pressure, lifting speed, clamping pressure, etc. by doing the indoor experiments, which supplied pipe free with guidance and basis; we further tested the performance of device by doing the field experiments, which verified the pipe free device can meet the demand of pipe free in oil field workover treatment.