Adsorption behavior of shale oil and water in the kerogen-kaolinite pore by molecular simulations

It is very meaningful to study the adsorption behavior of oil and water in shale nanopores in the context of enhanced oil recovery. Whereas, the investigation of shale and water adsorption in organic–inorganic pores is scarce. In this work, molecular dynamics (MD) simulations were used to study the adsorption behavior of multi-component shale oil and water in the novel kerogen-kaolinite pores. The adsorption characteristics of shale oil were studied through fluid density distribution, and the interaction energies between the fluid and the walls were calculated to describe the adsorption strength. The results show that different roughness, wettability, and polarity of the organic and inorganic walls caused the adsorption characteristics and strengths of shale oil and water to be asymmetrical. In the kerogen-gibbsite pore, water can form a film and adsorb near the hydrophilic gibbsite surface, while the shale oil exhibits heterogeneous adsorption on the other side of the pore. The presence of water will shield the influence of hydrophilic surfaces on the adsorption behavior of shale oil. Moreover, the active components of shale oil will form hydrogen bonds with water and regularly arrange near the water film, which makes it easy to capture the asphaltene clusters and block the pores. In the kerogen-siloxane pore, the adsorption peak of shale oil near the hydrophobic siloxane wall is much higher than that near the kerogen wall, while the adsorption strength is lower than that of the kerogen wall. Furthermore, we investigated the effects of water content, saline, and deprotonation (protonation) of active components on fluid adsorption behavior. Our study provides an in-depth understanding of shale oil and water adsorption in complex nanopores, especially the influence of wall wettability on the adsorption behavior.