Thestability Analysis Of Pre-bending Coiled Tubing In The Downhole

There are many advantages of Coiled tubing operating technique,and it has beenwidely recognized in the field of petroleum engineering.Pre-bending coiled tubing is anew technology in order to improve the life of coiled tubing. Now some scholars havestudied the mechanics analysis and life prediction for the above-ground part ofPre-bending coiled tubing technology.This paperestablish a dual nonlinear mechanicsanalysis model of the pre-bending coiled tubing in the downhole to quicken thistechnology development and application, to provide a theoretical basis for its securityapplications in field operations, and to optimize the design and to speed up thepopularization and application in oilfield.This paper analyzes the force and failure modes of the coiled tubing in the downhole,and predicts that might appear of failure modes of the coiled tubing in the downhole. Aswith the coiled tubing, there should be different failure modes of the pre-bending coiledtubing in the downhole in different load historical conditions,and mainly includes plasticdeformation, fracture, wear, corrosion, etc.This paper sets up a mathematical model of the pre-bending coiled tubing based onan analysis of the coiled tubing force and buckling state in the downhole, and thenonlinear mechanics of thin elastic rod and the statics moment balance theory.Solving themathematical model when the pre-bending coiled tubing with no weight and infinitesimalcurvature, and the result obtained with the previous findings consistent. Euler anglesingularity comes near the singular point value when we doing the integral, the numericalintegration will not be able to carry out, therefor Euler parameter is introduced.This article based on Lyapunov Stability, by analyzing, it is considered thatpre-bending coiled tubing stable equilibrium can be maintained for a straight rod under thecombined effects of the axial stress and lateral torque. Therefore, in downhole operationprocess, proper torque ensures that the pre-bending coiled tubing can smooth down intothe wellbore.