Wettability of rocks: Insights from an electrical double layer framework
Author Identifier (ORCID)
Stefan Iglauer: https://orcid.org/0000-0002-8080-1590
Abstract
A deep understanding of rock wettability is essential for elucidating multiphase flow dynamics in porous rocks and for applications such as hydrocarbon reservoir prediction and the safety assessment of subsurface carbon or hydrogen storage. However, wettability alterations driven by the formation of electrical double layers (EDL) at rock–brine interfaces remain poorly understood, highlighting the need for a clear theoretical framework. In this study, we develop a simplified and explicit model for rock wettability based on EDL free-energy, capturing the effects of interfacial electrostatics and brine compositions. Analysis of existing experimental data shows that the proposed model delivers superior accuracy, robustness, and practical applicability compared with the DLVO model. The model further reveals that nonpolar gas/brine/rock wettability depends on the square of the surface charge, surface potential, and pH, whereas oil/brine/rock contact angles are governed primarily by the absolute sum of the brine/oil and rock/brine zeta potentials. We also find that EDL compression plays a more dominant role in wettability alteration than interfacial tension under low-salinity conditions. The non-monotonic tendency of contact angle with salinity is divided into three regimes governed by the Jones-Ray effect, EDL compression and changes in interfacial tension, respectively. By incorporating the Hofmeister effect, our framework further explains ion-specific differences in wettability behavior. These findings provide a physics-based understanding of rock wettability and offer new insights into multiphase flow through porous rocks, low-salinity waterflooding, and CO2/H2 geo-storage.
Keywords
Electrical double layer, wettability
Document Type
Journal Article
Date of Publication
4-1-2026
Volume
131
Issue
4
Publication Title
Journal of Geophysical Research: Solid Earth
Publisher
Wiley
School
School of Engineering
Funders
National Natural Science Foundation of China (42407250, 42225702, W2521146, 42530708) / Natural Science Foundation of Jiangsu Province (BK20241211) / Opening fund of Key Laboratory of Earth Fissures Geological Disaster, Ministry of Natural Resources (JSDDY\u2010HJ\u2010D\u20102024\u2010007) / Opening fund of State Key Laboratory of Geohazard Prevention and Geoenvironment Protection (SKLGP2024K020)
Copyright
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Comments
Zhang, S., Tan, D., Zhu, H., Shi, B., & Iglauer, S. (2026). Wettability of rocks: Insights from an electrical double layer framework. Journal of Geophysical Research: Solid Earth, 131(4), e2025JB033401. https://doi.org/10.1029/2025JB033401