THE OVERALL PROCESS ANALYSIS AND EVALUATION OF PIN TAP TAPPING BASED ON THE ELASTOPLASTICITY MECHANICS IN OIL AND GAS WELLS

In oil and gas wells, because the selection of fishing pin tap lectotype and tapping parameters is blind, the refloatation period is long, and the chance of success is small. Based on the theory of large deformation and principle of virtual work, the mechanics model of fishing is established, and then, on the basis of Johnson-Cook empirical model, the elastoplasticity analysis and evaluation method in whole process of fishing pin tap are also proposed. In addition, the parameter sensibility of axial load, rotate speed, pin tap hardness, pin tap taper, thread pitch, friction coefficient is researched, which affects the ability of tapping and link strength of the new thread. In the end, the best parameters and pin tap type are obtained in fishing process, and then the largest lifting power is computed under these combinations. The results show that the methods of the analyzing and evaluating model are reasonable. And also, the research provides the scientific basis for the selection and optimization of pin tap, which has important engineering significance in increasing fishing efficiency and decreasing the chances that drilling tools drop out the wells.