高温高压气体在低含水率介质中迁移的数值模拟

Numerical simulation of gas transport at high temperature and high pressure in porous media with low water content

针对气液两相非等温渗流模型高度非线性的特点,发展了适宜的数值离散方法。根据相态转换准则和控制方程的性质,采用最低饱和度法简化算法。空间离散方面,使用有限体积法;时间离散方面,设计了一套包含合理求解顺序的Picard迭代法,解决了方程组强耦合的问题。利用上述数值方法对高温高压气体的迁移行为进行数值模拟,证明了气体在低含水率介质和等效孔隙度的干燥介质内的运动基本一致,并分析了空腔内的气液相态转变过程。在此基础上,研究了多孔介质孔隙度和渗透率对气体压强演化和示踪气体迁移的影响。研究表明,孔隙度越小(相同渗透率)、渗透率越高(相同孔隙度),示踪气体的迁移距离越远,并给出了估算不同孔隙度和渗透率下迁移距离的半经验公式。

In order to overcome the high nonlinearity of the model of non-isothermal liquid-gas two-phase flow in porous media,we have developed an appropriate discretization scheme.Based on the criteria of phase state transitions and the property of the governing equations,the minimum saturation method is adopted to reduce the complexity of the algorithm.For the spatial discretization,the finite volume scheme is used.For the time-domain discretization,a set of Picard iterative method which contains reasonable solving orders is designed to solve the strongly coupled equation systems.This numerical method is used to simulate the transport behavior of gas at high temperature and high pressure,demonstrating that the gas flow in a medium with low water content agrees well with that in a dry medium with an equivalent porosity.Phase transition between gas-liquid phases in the cavity is also analyzed.On this basis,the influences of porosity and permeability of porous media on evolution of gas pressure and transport of gas tracer are studied.It is found that the transport distance of gas tracer increases with decreasing porosity （for the same permeability） and increasing permeability （for the same porosity）,and semi-empirical formulas are given to evaluate the transport distance of different porosities and permeabilities as well.