Mechanism of Surface Particle Exfoliation and Its Impact on Water Flow in Shale Nanopores

Surface particle exfoliation occurs in diverse engineering applications. In shale gas development, high-pressure water injection creates fracture networks in tight shales while simultaneously inducing particle exfoliation from the reservoir rock. To elucidate the underlying mechanisms, we employ molecular dynamics simulations of the water flow within Illite shale nanopores. Our results reveal a four-stage exfoliation process, characterized by equivalent stress evolution, velocity distribution, and water-particle interactions. Initially, rough particles adhered to the Illite substrate in a layered structure. Exfoliation is initiated as water molecules infiltrate the interlayer from the inflow direction, inducing particle tilting. Velocity profiles demonstrate that vertical upward forces on the inflow side drive this initial detachment. Subsequently, particle displacement enabled water penetration from the opposite side, culminating in complete detachment. Throughout this process, equivalent stress distribution within the particle evolves consistently with the four identified stages, while the water-particle interaction energy progressively decreases. After detachment, the rough particle undergoes reorientation and migrates to the channel center, where it maintains a stable horizontal motion. Notably, the detached particle reduces the peak center-line velocity of the aqueous parabolic flow. Comparative simulations further reveal that particles with larger contact areas (A and C chains) exfoliate faster than B chain particles under identical flow conditions. These findings provide fundamental insights into particle exfoliation dynamics in nanoporous media, with implications for hydraulic fracturing optimization and soil erosion studies.