Evaluation and analysis method for air-tight seal special thread vibration fatigue failure test

Abstract

The invention discloses an evaluation and analysis method for an air-tight seal special thread vibration fatigue failure test. The evaluation and analysis method includes the steps: carrying out an evaluation method for an air-tight seal special thread vibration fatigue failure test on a physical sample; analyzing the maximum principal strain and the maximum principal stress of the thread structure and the main sealing surface in a load state according to finite elements; judging whether a material mechanical property change cyclic softening condition is met or not according to the stress state of the main sealing surface, carrying out a material cyclic stress-strain test by adopting a fatigue test axial force control method according to the maximum main stress change amplitude, and establishing a material yield strength variable function; and determining final yield strength, substituting the final yield strength into the finite element model to analyze sealing energy changes of mainseal contact pressure and length, comparing the sealing energy changes with internal pressure, determining seal integrity and thread structure fatigue failure performance, and completing air-tight seal special thread vibration fatigue failure analysis. According to the evaluation and analysis method, a basis is provided for sealing and structural integrity use and analysis and prediction of the air-tight seal special thread under the specific working condition vibration load.

Description

technical field [0001] The invention belongs to the technical field of petroleum and natural gas development, and in particular relates to a vibration fatigue failure test evaluation and analysis method of a special air-tight screw thread. Background technique [0002] Oil-casing gas-tight threaded connections are widely used in high-temperature, high-pressure, high-corrosion gas wells, and the failure of oil-casing threaded connections accounts for 90% of oil-casing failures. There are three types of oil tubing loads, static loads, dynamic loads, and thermal loads. Static load refers to the long-term axial compression, tension, internal pressure, external pressure and bending; dynamic load refers to the vibration fatigue load in the process of gas production; thermal load refers to the alternating tension and compression load caused by thermal expansion and cold contraction And the effect of high-temperature material performance degradation on the load-carrying capacity. ...

AI Technical Summary

Problems solved by technology

[0006] The technical problem to be solved by the present invention is to provide an evaluation and analysis method for the vibration fatigue failure test of the special thread of the air seal to ensure the integrity of the downhole pipe string structure and seal to solve the problems of the pipe string in the high internal pressure liquid. The thread connection failure problem in the process of fracturing and production gas recovery provides an evaluation and analysis method for the selection of oil field thread connection

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