Influence of cavity structure on fines migration and aggregation in rock fractures

Changes in rock fracture permeability due to fine particle migration affect gas production and stress distribution within a reservoir. Under stress, engineering disturbances, fluid scouring and erosion, and fracture protrusions are often sheared off, forming cavity structures within fractures. These cavities influence particle migration and aggregation within fractures. Numerical simulations of particle-laden fluid flow in fractures with circular, triangular, and rectangular cavity shapes were performed using the computational fluid dynamics–discrete element method. The results showed that the fluid velocity decreased with increasing cavity area, whereas increasing the inlet velocity of the suspension flow promoted fines aggregation and adhesion to fracture walls and reduced fine particle dispersion. A Belehradek function relationship between the fines velocity and quantity was attained when the inlet velocity of the suspension flow was greater than 0.25 m/s, the fines particle residence time was inversely correlated with the particle velocity. As the particle concentration increased, contact and aggregation within the channel increased, forming larger agglomerates that adhered to the walls, particularly in the cavity domains. Notably, compared with circular and triangular shapes, rectangular cavities showed reduced aggregation and adhesion.