Abstract
Underground gas storage as the main system of natural gas peak regulation, its construction demand continues to grow in the world. Different from other common oil and gas well strings, the service time of the gas storage string is longer and the service environment is worse, which poses a greater challenge to the integrity design of the string joint. In this paper, starting from the most important connection and sealing performance of the pipe string joint, aiming at the special threaded joint suitable for the gas storage pipe string, based on the analysis of the force and deformation of the gas storage pipe string, the joint connection strength and sealing performance of the pipe string joint under the axial load, internal and external pressure and long-term alternating load are considered. Based on the FINITE element model of VAM TOP special threaded joint, the deformation and sealing behavior of the joint under different composite loads were numerically simulated, and the variation law of joint connection stress and sealing contact pressure with load was obtained, and the most vulnerable failure position and the most dangerous working condition were analyzed.
Highlights
With the continuous growth of the demand for natural gas, the phenomenon of insufficient natural gas supply often occurs
Different from the common oil and gas well pipe string, the underground gas storage pipe string has been in service for more than 30 years, and the service environment is very bad
The alternating load caused by the long-term gas injection and production process poses a severe challenge to the design of pipe string, especially the design of pipe string joint
Summary
With the continuous growth of the demand for natural gas, the phenomenon of insufficient natural gas supply often occurs. In view of the above failures, it is necessary to study the connection and sealing integrity of threaded joint in order to maintain the operation safety of gas well in gas storage. The axial force of the gas storage pipe string is the sum of the superimposed axial force caused by dead weight, temperature effect, expanding diameter effect and ground stress during gas injection and production. Axial stress, MPa; MPa; Yp -- Pipe body yield strength, MPa. Because of the working condition of gas storage, it is easy to collapse under combined load. The compressive strength of tubing under combined load is: Pca. During gas recovery, axial pressure will be exerted on the tubing due to the decline of the inner layer of the well.
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