Prediction method for seal contact compression stress of special screw joint under thermal production condition

Abstract

The invention discloses a prediction method for a seal contact compression stress of a special screw joint under a thermal production condition. The method comprises the steps of firstly, numericallysimulating an initial room temperature and seal contact surface stress field distribution of the joint under an optimal make-up torque; secondly, indoors simulating an injection-production operation condition of a thermal production well, and representing temperature cycle features of a joint material in a long-time service process; thirdly, based on the temperature cycle features, building a mechanical model of strength and contact stress of the joint material; and finally, introducing the built material strength and contact stress model, building a radial main seal/axial auxiliary seal contact compression stress mathematic model of the joint in the long-time service process in combination with material anisotropy, and forming the prediction method for the seal contact compression stressof the special screw joint under the thermal production condition. The influence of temperature cycle in a multi-round injection-production operation process of thermal production on the contact compression stress is introduced; the prediction method for the contact compression stress is provided; and the solid technical support is provided for in-service casing string safety evaluation and leakage failure prevention and control of the thermal production well.

Description

technical field [0001] The invention belongs to the application field of oil and gas exploitation engineering, and in particular relates to a method for predicting the sealing contact pressure stress of special threaded joints in thermal recovery working conditions. Background technique [0002] The casing connection of thermal recovery wells mainly adopts API partial ladder thread, and its sealing performance mainly depends on the filled thread compound. The experimental results show that the thread grease filled at a temperature below 180°C can play a sealing role, but when the temperature rises above 200°C, the thread compound is prone to volatilization and deterioration, and the sealing performance of the connecting thread fails. [0003] The special threaded joint adds a radial main seal and an axial auxiliary seal torque shoulder structure in the structural design, no longer relying solely on the thread interference fit and the sealing effect of thread grease. That is...

AI Technical Summary

Problems solved by technology

At present, the design of casing strings in thermal recovery wells does not consider the temperature cycle characteristics of casing joint materials during long-term service, and the reduction of sealing contact pressure stress leads to the hidden danger of leakage failure of threaded connections

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