Dynamic Characteristic Analysis Of Gripping System Of Coiled-tubing Injector

Coiled Tubing Unit has the unique advantages of high working efficiency,low cost,simple operation and convenient transportation.The operating process has developed from simple sand washing and well repairing to well logging,acidification,fracturing,drilling and well drilling,etc.However,with the improvement of the scope and complexity of the coiled tubing operation,there are many different faults during the operations in the oil field.Such as the instability of injector head,coiled tubing skidding,pipe slipping and other phenomena;clamp block bites continuous tube,bite marks,scratches and other injuries;coiled tubing holding deformation,etc.These faults result in job failure or early fatigue failure of the coiled tubing(defective damage accelerated fatigue).The gripping system of Coiled-Tubing Injector,as the core mechanism of the injector head,provides the clamping force of the injector head to coiled tubing,and directly affects the performance of the injector head.Therefore,in order to reveal the law of action of the clamping system and the coiled tubing,and to improve the holding performance of the injector head,the dynamic characteristics of the gripping system of Coiled-Tubing Injector are studied in this paper.The main research contents are as follows:(1)Establish a dynamic model of the gripping system of Coiled-Tubing Injector.Based on the basic structural composition,working principle and engineering application of the gripping system of Coiled-Tubing Injector,the structural factors and working factors affecting the the gripping system of Coiled-Tubing Injector are analyzed,and the dynamic model of the the gripping system of Coiled-Tubing Injector is established based on certain assumptions.(2)Analyze and calculate the stiffness characteristics of the elastic elements in the dynamic model,and establish a hydraulic cylinder hydraulic spring model that drives the clamping system.Based on the extended transfer matrix method,the general transfer equation of the clamping system is established,and the dynamic response of each node of the clamping system is solved based on MATLAB programming.The amplitude of the clamping force fluctuation under different stiffness characteristics of the system is obtained.(3)the dynamic characteristics of the clamping system are analyzed in the AMESim software simulation environment,and the effects of different parameters onthe amplitude of the dynamic response fluctuation of the clamping force are compared.The study shows that the vibration parameters and the stiffness of the elastic cushion of the clamping system significantly affect the amplitude of the clamping force.Reducing the stiffness of the elastic pad in a certain range is an effective means to improve the clamping performance.At the same time,it is inferred that the hydraulic spring stiffness of the hydraulic cylinder can be increased to improve the dynamic performance of the clamping system.This study provides theoretical analysis for improving the gripping performance of the injector head,and provides guidance and scientific basis for improving the structural design of the gripping system and the coiled tubing operation process.