水层建库气驱水机理数值模拟

GAS-WATER DRIVE MECHANISM OF ESTABLISHING AQUIFER UNDERGROUND GAS STORAGE

国外已建成的储气库中,水层储气库数量居第二位,占12.5%。目前国内还没有水层储气库的建设实践,对水层建库机理的研究也较少。为此,采用数值模拟方法,以渗流力学为基础,建立数值模型来描述流体在地层中真实的物理过程。水层建库的主要过程就是气驱水的过程,采用气水两相模型,应用稳定的全隐式解法,对影响气水界面运动和驱替效果的影响因素进行了模拟分析。模拟发现:倾角较大,物性较好的水层以及较低的注气速率,可使气体前缘推进较均匀,气体驱替效率和波及效率较高;倾角较小,物性较差的水层及较高的注气速率,会使注入气体突进较严重,重力分异作用得不到很好的发挥,气水过渡带的宽度明显变大,波及效率和驱替效率都很低,不利于建库。

The amount of the aquifer underground gas storages (UGS) ranks second among the UGS being built in the world, accounting for 12.5 percent of the total. However, the aquifer UGS has never been built up in China till now and so the related researches on the construction mechanism could not be easily found out. So based on the theory of fluid mechanics in porous medium, this study established a model by numerical simulation to describe the fluid flow underground the reservoir. The gas drive water is a major step to construct the aquifer UGS. The influencing factors which have an impact on the gas/water contact (GWC) movement and the displacement performance were simulated and analyzed with this gas/water model through fully implicit method. According to the simulation results, the aquifer with relatively large angle and better physical property and low inject rate benefited the gas/water front drive and resulted in higher displacement efficiency and sweep efficiency. Nevertheless, the aquifer with relatively small angle and poor physical property and high inject rate could count against the injected gas fingering. In addition, the gravitational differentiation can not be well exerted and the gas-water transition zone will become wider, which will result in fairly low displacement efficiency and sweep efficiency, and will not be propitious for UGS construction. This study will play a significant reference and directive role in the construction of aquifer UGS.