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

Abstract

Abstract 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 (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 resultedmore » 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.« less

Authors:

Chang, Chun  ^[1];

• Search DOE PAGES for author "Chang, Chun"
• Search DOE PAGES for ORCID "0000-0001-9805-9067"

Kneafsey, Timothy J.  ^[1];

• Search DOE PAGES for author "Kneafsey, Timothy J."
• Search DOE PAGES for ORCID "0000-0002-3926-8587"

Tokunaga, Tetsu K.  ^[1];

• Search DOE PAGES for author "Tokunaga, Tetsu K."
• Search DOE PAGES for ORCID "0000-0003-0861-6128"

Wan, Jiamin ^[1]; Nakagawa, Seiji ^[1]

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+ Show Author Affiliations

1. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)

Publication Date:

Wed Sep 01 00:00:00 EDT 2021

Research Org.:

Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States)

Sponsoring Org.:

USDOE Office of Science (SC), Basic Energy Sciences (BES)

OSTI Identifier:

1841722

Alternate Identifier(s):

OSTI ID: 1821019

Grant/Contract Number:  

AC02-05CH11231; DE‐AC02‐05CH11231

Resource Type:

Accepted Manuscript

Journal Name:

Water Resources Research

Additional Journal Information:

Journal Volume: 57; Journal Issue: 9; Journal ID: ISSN 0043-1397

Publisher:

American Geophysical Union (AGU)

Country of Publication:

United States

Language:

English

Subject:

58 GEOSCIENCES; geological carbon storage; 2.5-D micromodel; immiscible displacement; mixed-wettability; distribution characteristics