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目前国内关于CO2咸水层封存尚处于先导性和试验性研究阶段,对超临界CO2注入过程中岩层力学响应和流体运移的理论与技术方面的认识还不完善。为研究CO2注入下岩层变形和流体运移,基于两相流动数学模型,给出了超临界CO2和咸水质量守恒方程;采用毛细压力和有效饱和度的关系式,将质量守恒方程变换成以毛细压力为变量的表达式,以便于考虑流体压力对岩层的影响。提出了无流体压力影响下的岩层力学本构模型,该模型能够同时考虑岩层的塑性变形和损伤。分析了两相流体-岩层相互作用机制:一方面,采用有效应力原理,考虑流体压力对岩层的力学影响;另一方面,通过岩层固有渗透率变化考虑岩层变形对流体运移的影响。
At present, the storage of CO2 saline layer in China is still in a pilot and experimental stage. The theories and techniques of rock mechanics response and fluid migration during the process of supercritical CO2 injection are still not perfect. In order to study the rock deformation and fluid migration under CO2 injection, the mass conservation equation of supercritical CO2 and salt water is given based on the mathematical model of two-phase flow. By using the relationship between capillary pressure and effective saturation, the mass conservation equation is transformed into The capillary pressure is the expression of the variable in order to consider the effect of fluid pressure on the rock formation. The constitutive model of rock mechanics under the influence of no fluid pressure is proposed. The model can simultaneously consider the plastic deformation and damage of rock strata. On the one hand, the effective stress principle is adopted to consider the mechanical influence of fluid pressure on rock strata; on the other hand, the influence of strata deformation on fluid migration is considered by the change of inherent permeability of rock strata.