Stress Analyses And Structure Improvement Research Of API Oil Tool Joint

Oil drill pipes are important tools for exploiting the oil and gas which connected the ground and underground together.The drill pipes were connected by the joint with the thread. Owing to the complicated situation and environmental factors,the joint was the weak link of the drill equipment. API drill pipe was often collocated for the screw stripped, perforated and twist off. The structural improvement of the drill pipe joints has been the key issues of the research.The FEM are the important tools for the drill pipe joints, established the FEM model according to the characteristics of the drill pipe joint,and the friction coefficient of the tool joint has been measured as the basis of analysis and ensure the reliability of the FEM results. The load distribution on joint threads has been analized,and the designed stress relieve structures can effectively improved the stress distribution which designed according to the results of the API. The new double shoulder tool joints has been analyzed, which increased the resistance of the torque and improved the stress distribution as for the API joints.The new joint has been obtained the patent. The joints have been put into production, and obtained better results. A structure of incline plane shoulder has been designed to improve the sealing performance of the joint and it improved the sealing ability effectively compared with the API joint.All the improvement processes were particularly calculated by the FEM and were validated by the tests from the factory which conformed to the actual circumstances.