流固耦合作用下含水层地下储气库天然气注采运移规律研究

针对地下储气库天然气注采运移过程中较少考虑应力场与渗流场相互耦合作用的不足,基于多孔介质弹性力学和渗流力学理论,建立了含水层型地下储气库天然气注采运移的流固耦合数学模型。首先通过对研究区块岩心开展三轴试验和应力敏感性试验得到储盖层的岩石力学参数和渗透率与有效应力的关系曲线,在此基础上建立了含水层地下储气库计算模型并对储气库天然气注采运移开展数值模拟研究,对比了耦合模型与传统渗流模型的计算精度;并重点讨论了储层渗透率、储层厚度、注入速率和排水量等参数对天然气运移规律的影响。计算结果表明:建立的流固耦合模型与传统渗流模型的计算结果具有较好的一致性,考虑流固耦合作用比非耦合作用下的储层压力增加1.04 MPa。含气饱和度随着储层渗透率和注入速率的增加而非线性增大,随着储层厚度的增大而非线性减小,随着排水量的增加影响不明显。

Study on the Migration Law of the Underground Gas Storage Reservoir in Aquifer in fluid-solid coupling

Very limited investigation has been done on numerical simulation of natural gas migration in sandstone aquifers with consideration of interaction between fluid flow and rock stress. The fluid-solid coupling mathematical model is established based on the poroelasticity theory and multiphase flow theory. A case study was carried out with the numerical model on the Jiangling sandstone aquifer in the Jianghan basin. The rock mechanics parameters and stress sensitivity of reservoir rock of Jianglin depression in Jianghan basin were obtained by experiment. On this basis, the natural gas migration law was analyzed and the result from the coupled model was compared with that from the traditional non-coupled model. The influences of permeability, thickness, injection rate and displacement on saturation ware studied. The calculation result indicates a good consistency between the coupled model and the non-coupled model. The pore pressure given by the coupled model is 1.04MPa higher than that by the non-coupled model. Saturation increases non-linearly with permeability and injection rate, and decreases non-linearly with reservoir thickness. The displacement has no obvious effect on the saturation.