页岩孔隙水中溶解气的主控因素与地质模型

Geological model of dissolved gas in pore water of gas shale and its controlling factors

页岩孔隙水中溶解气是目前研究较少的页岩气资源。通过PVTSim模拟软件对天然气在页岩孔隙水中溶解度进行了模拟。结果表明：页岩孔隙水中天然气溶解度受孔隙水盐度、地层温度和地层压力3者共同作用的影响,随孔隙水盐度的增大而降低,随页岩埋深的加大而升高。在超压条件下,其溶解能力大幅增加,更有利于天然气的保存。通过对川西南威远地区下古生界含气页岩的实例分析,发现在静水压力条件下,该套页岩孔隙水中甲烷溶解度可达3.79~11.34 m3/m3,页岩中溶解气含量可达0.018~0.054 m3/t。根据前人计算的游离气储量,认为孔隙水中溶解气可占游离气的2.2%~8.6%,是值得重视的页岩气资源。

Currently there is a lack of research on the dissolved gas in gas shale pore water.In this paper,the PVTSim software was used to simulate the solubility of natural gas in the pore water of shale deposit.The results show that the solubility of natural gas in pore water is controlled by the salinity of the pore water,formation temperature and pressure.It decreases with the salinity of pore water,and increases with the burial depth of shale deposit.The dissolved gas can be better preserved in overpressure conditions.A case study was conducted with the Lower Paleozoic gas shale in the Weiyuan area in SW Sichuan Basin.The simulation results show that the solubility of methane in shale pore water is in the range of 3.79-11.34 m3/ m3,and the reserve of the dissolved gas in the Lower Paleozoic shale is in the range of 0.018-0.054 m3/t.Combined with previous studies,it could be concluded that the amount of the dissolved gas is over 2.2%-8.6% of the free gas,indicating a considerable shale gas reserve.