The effect of mixed wettability on flow characteristics in porous media of ultra-deep gas reservoirs: Molecular dynamics simulations and numerical simulations

XD Lv and JM Sun and B Liao and CQ Fang and KH Lv and ZX Chen and JT Wang and JS Sun and P Chi and XJ Sun, APPLIED SURFACE SCIENCE, 654, 159541 (2024).

DOI: 10.1016/j.apsusc.2024.159541

Wettability is one of the critical factors affecting displacement efficiency and fluid distributions in ultra-deep gas reservoirs, and its accurate characterization is essential for improving gas reservoir recovery. The variation pattern of the wettability of minerals composition in high temperature and pressure environments in deep reservoirs still needs to be determined. In this paper, the variation pattern of mineral wettability under different temperature and pressure conditions is simulated based on molecular dynamics. Furthermore, the variation of a microscopic gas-water visualization distribution is calculated when the wettability of different components in porous media changes with temperature and pressure using the level set method. The results indicate that as the subsurface temperature increases or the pressure decreases, the hydrophilicity of minerals is enhanced, and having a particularly significant impact with temperature. As the proportion of a heterogeneous phase increases in a mixed wetting model, the influence of temperature takes a dominant position. The residual gas saturation is positively correlated with the content of the heterogeneous phase in the model. Moreover, under hightemperature conditions, the impact of wetting heterogeneity on gas-water distributions is lower than at room temperature. This work helps characterize the mechanism of gas-water transport under formation conditions, which is vital for ultra-deep gas reservoirs development and recovery enhancement.

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