Document Type

Journal Article

Publication Title

Fuel

Volume

399

Publisher

Elsevier

School

School of Engineering

Funders

King Abdullah University of Science and Technology

Comments

Usman, M., Yekeen, N., Ali, M., Ali, M., Keshavarz, A., Iglauer, S., & Vahrenkamp, V. (2025). Influence of organic matter and mineral composition on carbonate source rock wettability: Implications for CO2 geostorage. Fuel, 399, 135666. https://doi.org/10.1016/j.fuel.2025.135666

Abstract

Wettability is critical in determining carbon dioxide (CO2) behavior during geological sequestration in unconventional reservoirs. Unconventional reservoirs are compositionally heterogeneous, affecting CO2 plume migration, containment security, and storage capacity during geological sequestration. Previous studies on CO2 storage in unconventional reservoirs have primarily attributed to changes in organic matter content; however, this study examines how variations in the mineralogical and organic matter content combined affect wettability in CO2/brine systems under subsurface conditions. Three samples with varied mineralogy and TOC content were selected from a well drilled in Jordan source rocks—an immature analog of marine-derived, carbonate-dominated, Type IIS source rocks. Samples were analyzed using RockEval pyrolysis, X-ray diffraction, X-ray fluorescence, and Thermogravimetric analysis to characterize their organic and inorganic compositions. Samples were pyrolyzed at 600 °C to remove Volatile Organic Content (VOC), followed by a Brunauer–Emmett–Teller analysis and contact angle measurements (advancing: θa and receding: θr) via a tilted-plate goniometer using the sessile drop method. The results revealed that θa and θr increase with pressure (e.g., from 55° to 70° at 0.1 MPa to 119° to 121° at 20 MPa for organic-rich samples), whereas temperature effects depend on mineralogy, likely due to CO2/shale interfacial energy shifts from the changing CO2 density. Removing VOC reduced the brine contact angles (e.g., from 119° to 121° to less than 80° at 35 °C and 20 MPa), revealing a significant shift from CO2-wet to intermediate to strongly water-wet conditions. Additionally, the CO2 column height considerably increased after the VOC removal, with quartz-rich samples exhibiting the greatest effects (e.g., from –1050 to 3536 m at 35 °C and 20 Mpa). These findings demonstrate how geochemical variability driven by changes in rock mineralogy and organic matter content at subsurface conditions can affect CO2 storage capacity, plume migration, pore parameters, and competitive adsorption of CO2 on rock surfaces.

DOI

10.1016/j.fuel.2025.135666

Creative Commons License

Creative Commons Attribution-Noncommercial 4.0 License
This work is licensed under a Creative Commons Attribution-Noncommercial 4.0 License

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Link to publisher version (DOI)

10.1016/j.fuel.2025.135666