Pore-scale investigation of flow-induced particle detachment in unconsolidated sandstone

Abstract

Subsurface fluid flow induces particle detachment and alters the petrophysical properties of unconsolidated sandstone. Although particle detachment and changes in hydraulic conductance have been observed, the roles of interparticle cementation and fluid–solid coupling in controlling pore-scale particle detachment have not been quantitatively investigated. In this work, a computational fluid dynamics coupled with the bonded discrete element method was employed to quantify the dynamic process of particle detachment. A pore model of bonded particles was constructed to investigate how flow velocity and cementation strength control particle detachment in unconsolidated sandstone. The results show that a critical velocity exists above which particles start to detach from the pore skeleton. The critical velocity exhibits a linear correlation with cementation strength. An empirical detachment coefficient (De), which is proportional to flow velocity and inversely proportional to cementation strength, was proposed to characterize the detachment of particles. Specifically, three distinct detachment regimes are identified: no detachment (De ≤ 1.67 × 10−3), surface detachment (1.67 × 10−3 < De ≤ 3.33 × 10−3), and pore collapse (De > 3.33 × 10−3). Under surface detachment, the pore skeleton remains largely intact with only surface erosion. When pore collapse occurs, large clusters of particles detach, leading to significant alteration of pore structure. Moreover, the relative change in apparent hydraulic conductance decreases with increasing cementation strength but increases with flow velocity. A stepwise jump in hydraulic conductance is observed during the transition from surface detachment to pore collapse.