Structural Analysis And Study On Torsional Behavior Of Oil Casing Connection

Oil casing is an important equipment in oil and gas exploration and mining.Reasonable make-up torque has an important influence on the oil casing connection strength and sealing performance of oil casing connection.Due to the extremely complicated working environment,the failure of the connection caused by the weak torsion is more co mmon,so the torsional performance of its research has become particularly important.Based on the relevant theoretical achievements at home and abroad,this paper analyzes the structural characteristics,sealing mechanism and make-up torque of oil casing connection by analytic method,finite element method and full size method.The main contents and achievements include:1)Based on the analysis of the make-up torque formula recommended by the API standard,this paper provides a theoretical basis for the calculation of the make-up torque of the premium threaded casing connection.2)On the basis of analysis on the theory of thick-wall cylinder,the calculation method of interference values of the conical sealing surface of premium threaded casing connection has been derived.3)A two-dimensional axisy mmetric model of oil casing joint was established by finite element analysis software.The sealing mechanism of oil casing connection was studied with ?177.8 mm premium threaded casing connection.The concept of sealing strength was introduced,the influences of the tapered sealing surface and torque shoulder on the sealing performance of connection were analyzed,And the sealing structure parameters were optimized.4)The calculation method of the torque of the premium threaded casing connection is deduced,and the influence of the friction coefficient of the screw thread,the radial interference of the sealing surface and the axial displacement of the torque shoulder on the make-up torque is analyzed.5)The ?177.8 mm premium threaded casing connection is tested and make-up torque range was determined by the method of full size.At the same time,the sealing performance of the oil casing connection under axial tensile load is tested.The research contents and results of this paper can be helpful to the practical application of the oil casing connection.By using the calculation method given in this paper,the make-up torque of the special thread connection can be estimated well and can provide theoretical support for the mechanical behavior of the oil casing connection.