Fracture failure analysis of 5 “drill collar double shoulder external thread in a well

Abstract

This article analyzes a well using 5 “Based on the analysis of the chemical composition of the drill collar, mechanical property testing, metallographic structure analysis, fracture morphology and energy spectrum analysis, as well as the analysis of the stress, bending strength ratio, and double shoulder structure of the drill collar, combined with the deviation of the well section where the drill collar fracture occurred and the drilling pressure during drilling, it is clear that the main reason for the failure of the drill collar is that there is a large well deviation in the area and the drilling pressure is not properly reduced, resulting in The drill collar undergoes severe bending alternating stress and initiates fatigue cracks and propagates at the root of 1-2 threads at the large end of the external thread.