A New Phase Diagram for Fluid Invasion Patterns as a Function of Pore‐Scale Heterogeneity, Surface Roughness, and Wettability

Understanding how different flow patterns emerge at various macro‐ and pore scale heterogeneity,pore wettability and surface roughness is remains a long standing scientific challenge. Such understandingallows to predict the amount of trapped fluid left behind, of crucial importance to applications ranging frommicrofluidics and fuel cells to subsurface storage of carbon and hydrogen. We examine the interplay ofwettability and pore‐scale heterogeneity including both pore angularity and roughness, by a combination ofmicro‐CT imaging of 3D grain packs with direct visualization of 2D micromodels. The micromodels aredesigned to retain the key morphological and topological properties derived from the micro‐CT images.Different manufacturing techniques allow us to control pore surface roughness. We study the competitionbetween flow through the pore centers and flow along rough pore walls and corners in media of increasingcomplexity in the capillary flow regime. The resulting flow patterns and their trapping efficiency are in excellentagreement with previous μ‐CT results. We observe different phase transitions between the following flowregimes (phases): (a) Frontal/compact advance, (b) wetting and drainage Invasion percolation, and (c) Ordinarypercolation. We present a heterogeneity‐wettability‐roughness phase diagram that predicts these regimes.