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

Quantitative Characterization of Adhesion Work on Shale Surfaces and Discussion on the Influence of Roughness Based on Atomic Force Microscopy (AFM)

“…This development of oil wetness inhibits the formation of water wetness on rock surfaces, leading to a mixed wetting condition. 8 , 9 However, it is worth noting that there is an outlier in Figure 8 b, where the W ao of JA-3 is lower than the average level of the other samples, which is related to the degree of modification experienced by the rock. The primary space for crude oil in shale is in micropores.…”

“…This validates the argument in Section that dominance in oil wetness does not imply equal attraction capabilities of all points on the sample surface to crude oil; rather, it indicates that areas with strong oil wetness occupy more space. This development of oil wetness inhibits the formation of water wetness on rock surfaces, leading to a mixed wetting condition. , However, it is worth noting that there is an outlier in Figure b, where the W ao of JA-3 is lower than the average level of the other samples, which is related to the degree of modification experienced by the rock. The primary space for crude oil in shale is in micropores. − To validate this point, we used comprehensive methods such as low-temperature nitrogen adsorption and high-pressure mercury intrusion to evaluate the size and distribution of pores in the shale, combined with scanning electron microscope images to investigate the development of pore throats in the target area.…”

“…Globally, the increasing demand for petroleum resources and the depletion of conventional oil and gas reserves have led to significant attention for unconventional reservoirs. Among these, shale formations have garnered immense interest, with global technically recoverable resources reaching up to 700–800 billion tons, prompting extensive exploration. − However, this heightened interest is accompanied by significant challenges. , Regarding solid–liquid interactions, the heterogeneity of reservoir pore structures, variations in lithological segments, and mineral components can cause fluctuations in the adhesion work to crude oil, contributing to the complexity of mixed wetting distributions, − thereby rendering macroscopic evaluation methods insufficient for accurately characterizing microscopic adhesion phenomena . Thus, accurately assessing solid–liquid interactions at the microscopic level in shale formations, identifying the primary adsorption sites of crude oil, and exploring related influencing factors are crucial for understanding crude oil storage spaces and enhancing oil detachment efficiency.…”

“…28 − 32 Consequently, the resulting mixed wetting distribution varies due to different oil film binding sites in local spaces. 8 , 9 …”

“…Therefore, the distribution and density of surface charges will directly impact surface tension, consequently affecting wettability). Studies have shown that adsorbed asphaltene on solid surfaces can alter surface wettability. − Consequently, the resulting mixed wetting distribution varies due to different oil film binding sites in local spaces. , …”