Molecular dynamics simulation has emerged as a powerful tool to shed light on the fundamental mechanisms that govern fluid behavior across multiple phases, such as gas, liquid and solid, at the molecular-scale. In shale reservoirs, understanding nanoscale phenomena such as microscopic friction, oil-gas interactions during CO2 huff-n-puff processes, and the influence of co-solvents, is crucial for enhanced oil recovery and informing strategies for CO2 geological sequestration in shale. This paper explores the unique role of molecular dynamics simulations in revealing the microscopic mechanisms of fluid transport and enhanced recovery during CO2 injection, with particular attention to the effects of hydration film, CO2 affected areas and co-solvents. The regulatory mechanism of hydration films on the friction behavior of montmorillonite provides new insights into interfacial mechanics, with implications for the mobility of confined fluids. In tight reservoir systems, the microscopic oil recovery mechanisms of CO2 under varying sweep conditions water film thicknesses highlight the complexity of fluid displacement at the nanoscale. Furthermore, the co-injection of CO2 with selected co-solvents is shown to enhance both oil mobilization and carbon storage efficiency within shale nanopores, offering a promising pathway to improve recovery outcomes under diverse reservoir conditions. By providing a molecular-level understanding of these critical processes, this work lays the groundwork for bridging atomistic insights with field-scale applications for unconventional resources development. Document Type: Perspective Cited as: Bao, J., Du, J., Zhan, S., Wang, L., Luo, Y. A molecular perspective on the microscopic mechanisms of CO2 injection and water films in fluid transport and enhanced oil recovery. Advances in Geo-Energy Research, 2025, 16(3): 288-292. https://doi.org/10.46690/ager.2025.06.08

Dewatering and gas production are applied on a large scale in shale gas development. The fundamental mechanisms of water flow in shale nanoporous media are essential for the development of shale oil and gas resources. In this work, we use molecular dynamic simulations to investigate water flow in two different quartz surface ($(10\overline{1}0)\text{-}\alpha$ and $(10\overline{1}0)\text{-}\beta$) nanopores. Results show that the $(10\overline{1}0)\text{-}\beta$ surface exhibits stronger water molecule structuring with a structure arranged in two layers and higher first-layer adsorption density (2.44 g/cm³) compared to the ($(10\overline{1}0)\text{-}\alpha$ surface (1.68 g/cm³). The flow flux under the $(10\overline{1}0)\text{-}\alpha$ surface is approximately 1.2 times higher than that under the $(10\overline{1}0)\text{-}\beta$ surface across various pressure gradients. We developed a theoretical model dividing the pore space into non-flowing, adsorbed, and bulk water regions, with critical thicknesses of 0.14 nm and 0.27 nm for the non-flowing region, and 0.15 nm for the adsorbed region in both surfaces. This model effectively predicts velocity distributions and volumetric flow rates with errors generally below 5%. Our findings provide insights into water transport mechanisms in shale inorganic nanopores and offer practical guidance for numerical simulation of shale gas production through dewatering operations.