盐岩储气库蠕变损伤分析

Investigation on creep damage of natural gas storage in salt rock layer

通过对盐岩本构关系的实验研究,对Norton Power盐岩蠕变本构模型引入损伤变量,在损伤等效应力中引入考虑偏应力和围压影响的函数,建立了一种能反映盐岩蠕变和加速蠕变的本构模型。通过对某盐矿盐岩实验数据进行拟合,获得了本构模型的参数,理论曲线与实验曲线吻合得较好。通过三维数值模拟方法,应用该本构模型对某盐矿天然气储存库进行了数值模拟研究,探讨了该盐矿盐岩储气库最低内压工况下,腔周损伤区的扩展、变形规律及最长持续运行时间。研究结果表明:(1)盐岩本构模型在盐岩加速蠕变期具有较好的数值稳定性;(2)在最低运行压力下,腔周盐岩进入加速蠕变期后,储气库损伤区的扩展速度非常快,储气库最危险部位位于腔体顶部;(3)腔周盐岩进行加速蠕变期后,盐岩的腔体体积收敛变形主要表现为损伤蠕变体积收敛,稳态蠕变体积收敛趋于稳定;(4)该盐矿盐岩储气库在该压力下最长持续运行时间约为3个月。

Based on the mechanical test and the Norton Power law of salt rock, a new constitutive law of salt rock is presented. The new constitutive law can embody the steady creep and the accelerative creep of salt rock by importing the damage variable. The damage equivalent stress is the function of confining pressure and deviatoric stress in the new constitutive law, The parameters of the constitutive law were obtained by simulating the experimental data of salt rock in some salt mine. The theoretic results accord with the experimental results. By the three-dimension numerical method, the new constitutive law is programmed, The natural gas storage in the salt mine is analyzed by the new constitutive law. The evolvement law of damage bound and the displacement law around the natural gas storage is studied under the minimal natural gas storage pressure. The continuous operating time of the natural gas storage is also analyzed under the pressure. The study indicates that： （1） The presented constitutive law has good numerical stability during the accelerative creep. （2） The extension of the damage bound around the storage is very fast after the salt rock around the storage enter the accelerative creep phase under the minimal operating pressure. The most dangerous position of the storage is the top. （3） The steady volume convergence becomes steady and the damage creep volume convergence develops very fast after the salt rock around the storage enter the accelerative creep phase. （4） The continuous operating time of storage can＇t exceed three months under the minimal pressure.