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Impacts of Pore Network‐Scale Wettability Heterogeneity on Immiscible Fluid Displacement: A Micromodel Study
Author(s) -
Chang Chun,
Kneafsey Timothy J.,
Tokunaga Tetsu K.,
Wan Jiamin,
Nakagawa Seiji
Publication year - 2021
Publication title -
water resources research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.863
H-Index - 217
eISSN - 1944-7973
pISSN - 0043-1397
DOI - 10.1029/2021wr030302
Subject(s) - micromodel , wetting , porous medium , materials science , saturation (graph theory) , viscous fingering , capillary action , capillary number , displacement (psychology) , capillary pressure , composite material , porosity , mathematics , psychology , combinatorics , psychotherapist
The mixed‐wet nature of reservoir formations imposes a wide range of rock wettability from strong resident‐fluid wetting to strong invading‐fluid wetting. The characteristics of two‐phase flow in porous media composed of mixed‐wetting surfaces remain poorly understood. In this study, we investigated the displacement of resident ethylene glycol (EG) by hexane in two mixed‐wet micromodels of identical 2.5‐D geometry heterogeneity, with uniformly or heterogeneously distributed patches strongly wetting to hexane. These patches are mixed among pores with unaltered EG‐wetting surfaces. Along with control tests in the originally EG‐wet micromodel, we show the classic fingering and transitions in flow regimes at logCa (capillary number) from −7.2 to −3.9. Moreover, pore‐scale distributions of wettability and their spatial correlation influence displacement efficiency. In the two mixed‐wet micromodels, we found (a) an increase of steady‐state hexane saturation at the end of experiments by up to 0.12 in the capillary fingering regime and a decrease of at most by 0.06 in the viscous fingering regime, compared to the EG‐wet micromodel, and (b) dispersed and fragmented hexane distribution after displacement. Brine drainage during supercritical CO 2 (scCO 2 ) injections in these micromodels occurs with lower wettability contrasts, and under similar viscosity ratios and interfacial tensions resulted in higher displacement efficiency relative to displacement of EG by hexane. While mixed‐wettability can enhance displacement efficiency compared to uniform wettability, the dynamics of immiscible fluids in strong mixed‐wet reservoirs are expected to be less pronounced in contributing to the efficiency of geological CO 2 sequestration, oil recovery, and remediation of hydrocarbon‐contaminated aquifers.