Pore‐Scale Study of Fluid‐Fluid Interfacial Area During Primary Drainage in Porous Media

Abstract

We performed pore‐scale numerical simulations using the volume of fluid (VOF) method to investigate how displacement regimes, geometric disorder, and wettability influence fluid‐fluid interfacial area during primary drainage. We partitioned into two components: the advancing front , where both phases are mobile, and trapped wetting‐phase clusters . Results show that transitioning from stable displacement to viscous fingering enhances and its temporal fluctuations through complex front morphologies, while promoting larger trapped clusters that reduce . Increased geometric disorder broadens pore size distribution, further elevating and encouraging larger trapped clusters due to enhanced bypassing. Additionally, strongly water‐wet conditions generate highly curved menisci, increasing both components compared to weakly water‐wet conditions. The production rate of interfacial area, , nearly doubles under strongly water‐wet conditions and increases substantially with higher disorder and the onset of viscous fingering. These findings provide critical insights for predicting mass transfer, NAPL dissolution, and CO ₂ storage efficiency in subsurface systems.