Energy Conversion Reveals Regime Transition of Imbibition in a Rough Fracture

Abstract

As externally imposed flow rate increases during imbibition, viscous force increasingly dominates displacement over capillarity and imbibition shifts from capillary to capillary‐viscous regimes. Previous studies focused on capillary regime, lacking a fundamental understanding of regime transition. Here we study the imbibition transition via flow rate‐controlled experiments in a rough fracture. By analyzing energy balance in multiphase flow system, we find a fundamental link between regime transition and energy conversion. In capillary regime, surface energy is partially transformed into external work and an amount of 51−58% is dissipated via local rapid, irreversible events; while in capillary‐viscous regime, surface energy together with external work is transformed into kinetic and dissipated energies. This transition, corresponding to critical capillary number, is evidenced by quantitative analysis of invasion morphologies. Our work bridges the gap between energy conversion/dissipation and multiphase flow and has important implications for identifying imbibition regimes in enhanced oil recovery and geological CO2 sequestration.

High‐Speed Quantification of Pore‐Scale Multiphase Flow of Water and Supercritical CO2 in 2‐D Heterogeneous Porous Micromodels: Flow Regimes and Interface Dynamics

“…Furthermore, this trend implies that the leading edge of the CO 2 front advancing further downstream is not necessarily associated with the same finger but can instead alternate between fingers at different spatial locations as front advancement is more closely tied to local pore flow in the capillary fingering regime. Thus, these results reveal distinct pore‐scale invasion mechanisms for capillary and viscous fingering and are in agreement with previous experimental studies in rough fractures (Chen et al, ; Hu et al, ) and LBM simulations of flow in 3‐D porous rock media (Tsuji et al, ; Yamabe et al, ). For reference, x lead / L = 1 signifies the breakthrough of the CO 2 phase at the end of the porous section of the micromodel.…”

Phase diagram of quasi-static immiscible displacement in disordered porous media

“…2008; Cottin, Bodiguel & Colin 2011; Armstrong & Berg 2013; Bischofberger, Ramachandran & Nagel 2014; Hu et al. 2017 b , 2018 b ; Singh et al. 2017; Rabbani et al.…”

Influence of Capillarity on Relative Permeability in Fractional Flows

“…The mixed‐wet case exhibited more complex interface distributions with a heterogeneous distribution of fluid–fluid curvatures (Rücker et al, 2019). As seen in Figures 1d, 1e, and 1f, a wide range of curvature values are present, suggesting that capillary disequilibrium is more prevalent in mixed‐wet conditions (Hu et al, 2018; Reynolds et al, 2017). In the larger pores, we observed negative curvatures as the larger pores are oil‐wet; that is, water was present as spherical droplets with an interface that bulged into the oil phase (Lin et al, 2019).…”