Failure Analysis And Study Of Coiled Tubing Injector Under Special Working Condition

The coiled tubing has been widely used in oil and gas fields because of the low cost of operation,convenient of operation and the high efficiency. The injector head plays an important role in coiled tubing,so the performance of injector effect the performance of coiled tubing. When the coiled tubing working in special condition, the performance requirements for the injector is higher. If the injector performance can not reach the performance requirements of special condition, it will cause incalculable economic losses even life-threatening. So analysis of the injector failure for special working conditions has important theoretical significance and economic value.The special conditions of coiled tubing and failure of injector are analyzed. Firstly,the components of coiled tubing and the basic structure injector are analyzed. Secondly,the special working condition of coiled tubing is analyzed. It shows that coiled tubing has variety of special condition. Finally, analyze the possible failure of injector. It can obtain that it should focus on the analysis of chain failure under blowout-related condition, tube-clamping block system failure under sticking condition and tubing buckling failure under wellbore plugging condition.The chain failure under blowout-related condition is analyzed. Through the fatigue failure analysis of chain plates and rollers, the maximum lifting speed can be acquired. Through the analysis of the contact of sprockets and rollers, the failure cause is obtained.The failure of tube-clamping block system under sticking condition is analyzed. The critical lifting force and critical clamping force is calculated with theoretical analysis under sticking condition. Through finite element analysis of partial load clamping and dislocation dripping clamping, it can obtain the extent of damage to the tubing. The method to improve clamping performance is proposed and analyzed.The buckling of unsupported tubing is analyzed. Through comparative analysis of linear buckling and nonlinear buckling, the critical buckling load is obtained. It studies the factors affecting the tubing buckling, including tubing wall thickness, diameter size and tubing unsupported length. It also analyzes the impact of various factors on the critical buckling load.