Study On Coupling Dynamics And Operation Efficiency Optimization Of Marine Coiled Tubing Repairing Pipe Strings

In recent years,with the continuous development of ocean oil industry,offshore production facilities have gradually moved from shallow water to deep water.The coiled tubing technology has made great attention of the oil and gas industry,it has been widely used on land,such as drilling,sidetracking windows,salvage,sand washing and other workover operations.If the Coiled tubing can be applied to the sea,it will be a promising work technology.But the shortcoming of coiled tubing is also obvious.Its rigidity is small,so when operation it is easy to cause sinusoidal,spiral buckling,etc.As the increasement of the water depth and the disturbance of wind,waves,currents,etc.,it is likely to cause coupling vibration and lead to failure of operation,and even induce accidents,therefore,it is necessary to systematically research the mechanical behavior characteristics of the pipe-in-pipe system under the marine environment.This paper uses the micro-element method to analyze the riser and coiled tubing based on the D'Alembert principle.It considers the contact force and friction force,establishes the coupled system dynamics model,and theoretically analyzes the cause of the coupling effect.The paper uses the tube-in-tube contact unit provided by Abaqus to simulate the contact between the inner and outer pipe,the coupling model is modeled and solved using the finite element method.At the same time,the transverse vibration model of the riser in the pipe-in-pipe system is established.The frequency characteristics and vibration response of the riser are solved by the resonance method and the difference method,and the results are verified by Abaqus simulation results.Comparing the riser system with the pipe-in-pipe system,it founds that the coiled tubing has a great influence on the system.Based on the calculation model,the effects of top tension,additional mass,drilling fluid density,pipe wall thickness and length on the frequency characteristics of coupling system have been researched.The CT injection force,the riser top tension,the top offset of the system,the annulus and the friction coefficient between the inner and outer pipe,the density of the drilling fluid and the parameters excitation frequency of the floating body for the work efficiency and operational safety impact have been analyzed.And the effects of uncontrollable environmental factors such as ocean depth,current velocity,wave period and wave height on the coupling system have been researched.Finally,in response to the average sea conditions in the South China Sea in recent years,this paper designs experimental data,and combines with neural network and genetic algorithm to optimize the efficiency of work,which provides a certain reference for practical work.