Consider The Residual Strain Of The Coiled Tubing Downhole Buckling Behavior Of Theoretical Research

The problem of the behaviors of coiled tubing down-hole buckling is the key of the success of coiled tubing down-hole operation. Presently, the study did for it just directly used the results of study buckling behaviors on drilling pipe, casing string, conventional oil tubing to deal with coiled tubing; many filed cases indicate that to do so will give big differences. Because of residual strain, coiled tuning has special down-hole buckling behaviors. However, theoretically researching the down-hole behaviors of coiled tubing with residual strain has been facing with much difficult problems on researching method, mechanics and mathematics all the time. No good improvements and progresses have been made; no mature theoretical researching methods have been got.Based on the formers' results of study buckling behaviors on drilling pipe, casing string, conventional oil tubing to coiled tubing, this thesis theoretically studied coiled tubing with residual strain buckling in straight deviated well and constant-curvature well. Big progresses have been made on researching methods and solving skills of mechanical-mathematical problems. The main studying results of this thesis as followings:1) Though analyzing the function of the gripper in the coiled tubing equipment, that it can greatly change the helical bending stain from the coiled tuning reel has been found. After acting with the gripper, the initial configuration of coiled tubing in the well assumes a sinusoidal configuration. By the assumption the effect of coiled tuning's residual strain has been considered. Using a tangible, easily descriptive initial configuration to consider the bodiless, complex and difficultly descriptive residual strain 。2) Energy method has been used to analyze the behavior of coiled tubing down-hole buckling. The mathematical modes of the initial sinusoidal configuration and the final buckling configuration have been successfully made.3) From the basic mechanical theories, the formula of bending stain energy, the formula of work done by the external force and the formula of work done by the weight component have been derived.4) According to the principle of minimal potential energy and the principle of conservation of energy. The sinusoidal buckling and helical buckling equilibrium...