Impacts of Pore Network‐Scale Wettability Heterogeneity on Immiscible Fluid Displacement: A Micromodel Study

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...

Full description

Saved in:
Bibliographic Details
Published in:Water resources research 2021-09, Vol.57 (9), p.n/a
Main Authors: Chang, Chun, Kneafsey, Timothy J., Tokunaga, Tetsu K., Wan, Jiamin, Nakagawa, Seiji
Format: Article
Language:English
Subjects:
2.5‐D micromodel
Aquifers
Brines
Capillary flow
Carbon dioxide
Carbon dioxide fixation
Carbon sequestration
Displacement
distribution characteristics
Efficiency
Ethylene glycol
Fluids
geological carbon storage
Heterogeneity
Hexanes
Hydrocarbons
immiscible displacement
Miscibility
mixed‐wettability
Oil recovery
Porous media
Reservoirs
Saturation
Viscosity
Viscosity ratio
Wettability
Wetting
Citations: Items that this one cites
Items that cite this one
Online Access:Get full text
Tags: Add Tag
No Tags, Be the first to tag this record!
Description
Summary: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 CO2 (scCO2) 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 CO2 sequestration, oil recovery, and remediation of hydrocarbon‐contaminated aquifers. Key Points Fingering flow of hexane–ethylene glycol was investigated in mixed‐wet micromodels with bimodal contact angle distributions at 47° and 145° Mixed‐wettability diminishes displacement efficiency when contact angles vary beyond 90°, and at low capillary numbers We proposed a new set of capillary numbers to characterize the displacement and fingering flow in strong mixed‐wet systems
ISSN:0043-1397
1944-7973
DOI:10.1029/2021WR030302