Pore-Scale Imaging and Analysis of Wettability Order, Trapping and Displacement in Three-Phase Flow in Porous Media with Various Wettabilities

Abstract Three-phase flow in porous media is encountered many applications including subsurface carbon dioxide storage, enhanced oil recovery, groundwater remediation and the design of microfluidic devices. However, pore-scale physics that controls three-phase under capillary dominated conditions still not fully understood. Recent advances three-dimensional imaging have provided new insights into flow. Based on these findings, this paper describes key processes control trapping a system, namely wettability order, spreading wetting layers, double/multiple displacement events. We show medium containing water, gas, behaviour controlled by wettability, which can either be water-wet, weakly oil-wet or strongly oil-wet, gas–oil miscibility. provide evidence that, for same state, events are different near-miscible conditions—where interfacial tension ? 1 mN/m—compared to immiscible conditions. In water-wet at conditions, water most-wetting phase residing corners pore space, gas most non-wetting occupying centres, while intermediate-wet layers sandwiched between gas. This fluid configuration allows double trapping, result more than two-phase At appear become neutrally each other, preventing from layers; instead, compete occupy centre larger pores, remains connected corners. rapid production since it no longer confined movement thin layers. order oil–water–gas, least wetting, promoting centres during water-alternating-gas injection. altered as becomes phase, high recovery factor restricting reservoir. Moreover, we predicted, but hitherto reported, systems oil–gas–water, wetting. progresses through space disconnected clusters multiple displacements; therefore, injection large amounts disconnect unnecessary. place analysis practical context discussing implications storage combined with before suggesting topics future work.