Jixie qiangdu (Jan 2023)
RESEARCH ON FAILURE MECHANISM OF FRICTION-WEAR OF TUBING STRING IN 3 H CURVED WELL (MT)
Abstract
Aiming at the wear failure of tubing string caused by the nonlinear flow-induced vibration（FIV） in high-temperature, high-pressure and high-yield（3H） gas wells, the nonlinear FIV model of tubing string was established using the element method, energy method and Hamilton variational principle, which considered the changes of wellbore trajectory, wellbore temperature/pressure, and contact of casing. A simulation experiment of the tubing string vibration was conducted to verify the correctness and validity of the nonlinear vibration model. Based on the White-Fleisher wear theory, a calculation method for the wear amount and depth of tubing string in 3H gas wells is proposed. The wear unit test is carried out, and the friction coefficient and wear efficiency are determined. On this basis, the influence of production rate, well angle, well section length, packer position and centralizer position on wear characteristics of tubing is systematically analyzed. The safety control methods of tubing string were proposed, namely, which shown that, firstly, with the increase of production rate, the wear life of the string decreases, and there is a sudden value, which can be determine using the analysis method, so that the field production allocation should be far away from the sudden production rate. Secondly, in the well trajectory design, the length of vertical well section should be reduced, and the length of build section and the angle of stable inclined section should be increased. Thirdly, there is an optimal position of packer and centralizer in the field, which is related to the well structure, string structure and downhole tool size, and can be determined by the proposed analysis method to guide the design of packer and centralizer. The research results can effectively improve the service life of tubing string in 3H gas wells.
