A dynamic model and mechanical properties of the fishing system for high-inclination wells

High-inclination well shave large hole deviation angle and complex structure. The fishing system of high-inclination wells faces some theoretical problems that affect the reliability of fishing operations, and need to be overcome. Currently, less research results in terms of the dynamics theory have been obtained for the fishing system of high-inclination wells. As a result, it is impossible to analyze the mechanical characteristics of the fishing system and study the improvement of fishing technology based on basic theories. This paper proposes a series of methods such as steel wire-tubing contact analysis and pressure drag calculation of tubing, aiming to establish a dynamic model for the steel-wire fishing system of high-inclination wells that comprehensively considers the interaction between wellhead auxiliary device, steel wire, and fishing device. Based on the finite difference method, and the Gaussian elimination method in combination with the iteration method, the model was solved; the validity of the model was verified using the on-site measurement results. According to the dynamics model, a study is performed on mechanical characteristics of the fishing system of high of the fishing system; it finds the load fluctuation law of fishing tool string in the processes of tripping in, delivery, lifting, and fishing, and reveals the influence mechanisms of hole deviation, hole depth, wellbore trajectory, stroke, and the geometric parameters of fishing device on undershooting speed.