考虑渗流-应力耦合作用的层状盐岩界面裂缝扩展模型研究

Analytic model for interface crack propagation of salt rock with interlayer under coupled mechanical-hydrological environment

针对中国地下油气储库建设中所出现的含夹层盐岩问题,基于黏结裂缝模型,构建一种可以考虑层状盐岩地层界面启裂、裂隙扩展和流体渗漏的黏结单元,导出地层界面损伤演化方程、裂隙扩展准则以及缝内流体流动方程,建立考虑渗流-应力耦合作用的层状盐岩界面裂缝扩展模型,通过典型算例验证模型的有效性。研究层状盐岩地层界面启裂与裂隙扩展过程。研究结果表明:地层的渗透性和裂缝面漏失系数对地层界面裂隙扩展有明显影响,地层渗透性系数越小,地层开裂程度越大;而裂缝面漏失系数越大,地层开裂程度越弱,但流体渗漏程度加大。

According to the reality of bedded rock salt and clay interlayer for oil or gas storage in China, the cohesive element built in bedded salt rock was used to simulate the initiation, propagation and fluid seepage resulted from hydraulic loading by the cohesive zone model. The damage evolution equation, crack propagation criterion and fluid flow equation of interlayer were established. Based on the fluid-solid coupling theory of rock, the coupled interface crack propagation model of salt rock with interlayer was put forward and a typical example of application was presented to verify the validity of the model. Then, the crack propagation process of salt cavern was studied and the influence law of pore pressure, injection pressure and crack propagation was discussed in different conditions. The results show that the permeability of rock and leakage coefficient of crack has significant effects on the condition of crack propagation. The condition of crack aggravates with low permeability of rock and reduces with high leakage coefficient.