The Safety Analysis And Evaluation Of Gas Injection Tubing Design In The Underground Gas Storage

With the "post-oil era" coming,the development and utilization of natural gas grows rapidly.The use of natural gas is often influenced by outside factors such as geography,climate and time,which makes it often appears obvious peak season and off-season.Underground gas storage has become the world's leading natural gas storage methods so far because of its the advantages of cheap price and large gas storage.However,the high speed gas flow effects on the gas injection tubing for a long time in the process of underground gas storage operation,it can easily lead to vibration,so the safety analysis and evaluation of gas injection tubing design is of great significance to underground gas storage.This paper is based on the mechanism that gas flow induced gas injection tubing vibration.According to the theory of computational fluid dynamics,tubing mechanics and vibration mechanics,we adapt finite element method to carry out the research of high speed gas flow would lead to the gas injection tubing vibration,especially exploring the tubing wall pressure distribution while the natural gas flowing through the gas injection tubing bending section and cross-sectional change area.Then the dynamic response analysis of the gas injection tubing bending section is conducted by using flow field analysis data to determine the stress state and dynamic characteristics of the tubing.We also combine the analysis results of stress and deformation to predict the fatigue life of the tubing.Finally,the safety analysis and evaluation of gas injection tubing design is carried out in order to reduce damage and extend the service life of the tubing.The results shows : direction of natural gas flow is changed in the gas injection tubing,leading the velocity,pressure,turbulence kinetic energy and vorticity field to change,generating swirl here at the same time.When the tubing has been subjected to external excitation force,its stress and deformation suffer tubing dynamic load changes and are consistent with the trend of the pressure changes.We also derived fatigue life prediction formula of gas injection tubing,draw the cumulative fatigue life using coefficient and dangerous position at the location of the gas injection tubing so as to put forward the measures to prolong the safety running time.These conclusions derived provide theoreticalbasis for gas storage gas injection tubing design and field operations.