Failure analysis of long round thread in horizontal well casing under multi-axis loading

The casing is subjected to complicated forces underground, and the threaded joint of the casing is the weak link of the casing. becoming more and more severe, various kinds of failure accidents often occur in practical use. Therefore, in view of the casing thread fracture failure during the process of volumetric fracturing in well W of an oil field. The finite element model of 5-1/2"API casing long round threaded joint was established in this paper, ABAQUS software was used to simulate and analyze the stress and deformation of casing thread under the loading state of overlock, axial tension and pressure, and fracturing internal pressure. The results show that the stress distribution of teeth is reasonable. Under the condition of axial tension and compression, the maximum stress of casing thread exceeds the yield strength into plasticity and causes damage. However, when fracturing and stimulation technology is implemented, the stress of the collar and casing body increases significantly, and the fracture is caused by fatigue and extended fracture under the alternating fracturing load. The finite element analysis results are consistent with the field failure results. Study the influence of downhole complex working condition on casing thread by simulation, which is of great significance to the protective casing.