盐岩地下储气库套管运行安全的可靠性分析研究

Reliability analysis of casing of underground salt rock gas storage during operation period

盐岩因其具有良好的蠕变特性、低渗透性以及损伤自我恢复特性成为国际上公认的最理想能源地下存储介质。在盐岩地下储气库运营过程中储库套管受到储气内压、材料参数和几何尺寸等不确定性因素的影响,为了评价这些随机风险因素对储库套管结构运行安全的影响,建立了盐岩储气库的套管结构模型和基于VonMises屈服准则的套管结构功能函数,根据建立的结构模型和结构功能函数,应用响应面法结合蒙特卡洛抽样计算获得储库在高压和低压运行条件下套管结构可靠度的变化规律。可靠性分析表明,为保证套管运行安全,储库最低运行内压应大于3 MPa,最高运行内压应小于22 MPa,套管靴距离储库腔顶的距离应大于10m,并应适当加大套管的壁厚和减小套管的内径。

Salt rock is internationally recognized as the most ideal energy underground storage medium because of its good creep properties,low permeability and damage recovery characteristics. Casing structure of gas storage in underground salt rock is affected by internal pressure, material parameters and geometric size of casing which are uncertain during the operation process of gas storage.In order to evaluate effects of these random risk factors on operation safety of casing structure, a mechanical model and the structure function of casing based on Von Mises yield criterion have been established. According to the established mechanical model and structure function, the change laws of reliability of gas storage casing under the high pressure and low pressure conditions are obtained through the response surface combined with Monte Carlo sampling. Reliability analysis shows that the minimum operating pressure of gas storage should be greater than 3 MPa, the maximum operating pressure of gas storage should be less than 22 MPa, the distance between the casing shoe and the gas storage cavity should be more than 10 m. In order to ensure the safety operation of the gas storage casing, it is very important to appropriately increase the casing wall thickness and decrease the diameter of casing.