Pore-scale study on formation bond breakage and sand production induced by fluid flow

Formation bond breakage and sand production resulting from fluid flow are common in groundwater flow, petroleum engineering and underground energy storage. Previous studies have primarily focused on macroscopic observations of sand production or empirical correlations, with limited insight into the microscopic mechanisms governing particle detachment and bond breakage. To address this gap, the study develops a coupled computational fluid dynamics and discrete element method framework to directly simulate fluid–solid interactions at the particle scale and systematically analyze the effects of fluid velocity, viscosity, and formation bond strength. The increases in fluid velocity and viscosity lead to a rise in the drag and pressure gradient forces, causing the contact stress between particles to gradually increase and finally exceed their bond strength threshold. Specifically, the sand production and bond breakage remain stable until the flow rate increases to 2.5 m/s; thereafter, they increase significantly from 0.64% and 8.7% to 1.12% and 69.6% at 3.5 m/s. As fluid viscosity rises from 0.5 to 4 mPa s, sand production increases from 0.7% to 2.0%. The resistance of porous media to fluid-induced erosion improves significantly as the bond strength increases from 0.05 to 0.2 MPa, resulting in a sharp decrease in sand production and bond breakage from 1.5% and 82.6% to 0.24% and 5.1%, respectively. By quantitatively and visually revealing microscopic bond breakage and particle migration, this study provides guidance for mitigating formation damage and sand production.