The Research Of Oil Tubing-Cutting Technology By Abrasive Water Jet

Handling the accident of rod sticking and pipe sticking in downhole by conventional way produceslong processing cycle and poor effect. To seek a safe and efficient way, abrasive water jet cuttingtechnology is proposed on the basis of full investigation of the related work at home and abroad.Abrasive water jet cutting technology can get high cutting efficiency, convenient and safe operation andregular incision. The paper designs a kind of abrasive water jet cutting device for drill pipe and tube(≥2-7/8"), whose cutting head is droved by turbine. According to numerical simulation, it is found thatwhen the rotational speed of cutting head is over100rpm, jet spray and the worn of seals are serious andthe impact force is greatly decreased. So, it is necessary to design speed control device.According to the damping oil deceleration device’s disadvantage of unreliability and high startingtorque, this paper presents a new design of an electromagnet deceleration speed control device, which iscomposed of the magnetic stator installed on the central shaft and loop stator installed on the tool caseand connected with resistors. In the working process of cutting device, the rotation of central shaft isdrove by turbine. Relative rotation is generated between the rotor and the stator. Electromotive force isgenerated by cutting magnetic induction line. Electromotive force is converted to heat through theresistor, thereby part of torque is consumed. The greater the relative rotation speed, the faster the loopcutting speed of the magnetic induction lines we can get. The electromotive force is larger, i.e. the greaterthe electromagnetic drag torque. When the electromagnetic resistance torque and the torque reachequilibrium, the rotation speed of the central shaft reaches a stable value. In the premise of fixed loopnumber and permanent magnet number, the electromagnetic moment of resistance is changed byadjusting the resistance value of external resistors, in order to achieve precise speed control of the centershaft.Experiments are carried out in submerged condition to study the effect of various parameters on thecutting efficiency, including number of nozzles, rotation speed of cutting head, standoff distance, duration of cutting. The results show that increasing the quantity of nozzle and reducing the standoffdistance can obtain higher cutting efficiency. With the increase of cutting time, the cutting depth becomeslarger. Under the experimental conditions, the optimal rotational speed of the cutting head is21rpm. Also,the cutting device designed in this study can work smoothly and reliably, the electromagnet decelerationspeed control agencies can precisely control the rotation speed of the cutting head. The results obtainedin this study offer a new way to handle sticking accidents in downhole and expand the application ofabrasive jet technique in this field.