Research On The Electrical Arc Cutting Technology And Cutting Equipment For The Downhole Tubing

With the development of oilfield exploitation,the phenomenon of deformation and misalignment of downhole tubing in oilfields around the country has also increased year by year.In order to meet the needs of workovers,many different new processes and tools have emerged.Among them,tubing cutting is a more effective way to cut off the tubing at the maximum and prepare for the later salvage work.Therefore,it has systematically and deeply carried out theoretical and experimental research for downhole tubing cutting,developed a set of cutting equipment for downhole tubing and summarized a process suitable for cutting tubing,and achieved some important theoretical significance and engineering application value.In this paper,it conducted deeply research around domestic and international research status of cutting technology and cutting tool for downhole tubing.Then proposing a method for cutting downhole tubing based on arc cutting.The high temperature generated by arc discharge between electrode and tubing is used to melt the material.Compared with traditional cutting technology,arc cutting technology has no mechanical cutting force,high cutting efficiency,low electrode loss rate.A mechanical system with compact structure and realized arc cutting downhole tubing has been developed.It mainly includes upper supporting mechanism,rotating mechanism,feeding mechanism and lower supporting mechanism.The dimensions of the upper and lower supporting mechanisms and the effective length of the electrodes are calculated,and the output torque of the rotating motor is checked.At the same time,the motor uses magnetic driving to seal and it realizes the sealing and overload protection of the downhole motor.The control system for arc cutting equipment based on STM32 is developed,mainly including three parts: cutting power,main control system and detection system.It realizes lowering control,rotation control,electrode automatic feeding control,cutting power arc ignition control and auxiliary functions control of cutting tool.And the electrode motion control strategy based on real-time detection of cutting voltage and current is proposed.At the same time,arc ignition circuit,gap voltage detection circuit,current detection circuit and display circuit have been designed.The temperature field model of arc cutting tubing based on heat conduction theory is established.The Gaussian heat source is used to simulate the process of cutting tubing.The effects of cutting speed,electrode diameter and cutting current on the temperature field distribution of arc cutting are analyzed.The optimal cutting parameters are determined and the cutting effect under the optimal cutting parameters is simulated.And the process of temperature changing over time are analyzed,including many slit nodes of inner diameter,outer diameter and radial.A tubing cutting experimental platform is built.The experimental research on arc cutting technology is carried out.The effects of working medium,electrode material and electrode polarity on electrode loss rate and electrode utilization rate are studied.At the same time,the effects of different cutting parameters on the slitting morphology and electrode morphology are analyzed.Then,a 3-1/2in tubing is cut.The result shows that the arc cutting method has high cutting efficiency and fine cutting effect.