Analysis of Over-Torque Failure Characteristic of Tool Joints

Abstract Increasingly demanding drilling conditions and progressive drilling technology put forward new requirements for the torsion performance of tool joints. Over-torque failure of tool joints in downhole occurs frequently, resulting in huge economic losses. It is of great significance to analyze the mechanism of over-torque failure of the tool joint. This mechanism can help to selection of the tool joint and improve the design of the tool joint. In this paper, three dimensional elastic-plastic finite element models of single-shoulder tool joint and double-shoulder tool joint are established. Based on ABAQUS, the stress characteristics of tool joints under working torque are analyzed, and the mechanism of over-torque failure of API single-shoulder tool joints and double-shoulder tool joints is revealed. The result shows that there is a serious stress concentration phenomenon in both single-shoulder tool joints and double-shoulder tool joints, which restricts the performance of tool joint. The stress distribution of the tool joint should be homogenized in the design of the new type of tool joint, so as to improve the performance of the tool joint.