Study on fracture behavior of drill pipe body with surface double cracks
Drilling pipe leakage is the most common failure form of drilling pipe in service,and the expansion of sur-face crack of drilling pipe is the direct cause of drilling pipe leakage.In order to evaluate the safety performance of drill pipe with multiple cracks on the surface,a finite element model of double cracks on the surface of drill pipe was established by taking the wellhead section of G105 drill pipe of an ultra-deep vertical well as the research object.The effects of crack spacing,crack size and strike on the J-integral at the leading edge of the circular main crack un-der tensile and torsional loading were analyzed.The results show that the circumferential secondary cracks arranged in the axial direction are relatively the safest,which can greatly reduce the J-integral of the leading edge of the main crack.The circumferential secondary cracks arranged in the circumferential direction are the most dangerous,which can greatly increase the J-integral of the leading edge of the main crack.The axial secondary cracks can increase the J-integral of the leading edge or part of the leading edge of the main crack in the drill pipe,but the increase is much weaker than that of the circumferential secondary cracks.The influence intensity of secondary cracks on the leading edge J-integral of the main crack decreases with the increase of the distance between two cracks and the decrease of the size of secondary cracks.Therefore,the influence of secondary cracks should be considered when the size of sec-ondary cracks is large and the distance between them is relatively close.When the size of the secondary crack is small or the distance is long,the secondary crack can be ignored,and the model is simplified to a single-crack drill pipe model for analysis.
万方数据
维普
