Reexamining supercritical gas adsorption theories in nano-porous shales under geological conditions

Fengyang Xiong, Gernot Rother, Yiwen Gong, Joachim Moortgat

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22 Scopus citations

Abstract

Adsorption is an important phenomenon in surface chemistry, especially for nano-porous shales. In the shale gas-in-place, adsorbed gas could contribute up to 85%. However, adsorption is hard to quantitatively characterize due to different adsorption mechanisms, patterns, surfaces, and pore sizes. Moreover, key thermodynamic parameters, such as the enthalpy of adsorption, are challenging to determine due to uncertainties in adsorbed gas densities used in constructing absolute isotherms. In this paper, we revisit the Brunauer, Emmett, and Teller (BET) model, analytically simplify Ono-Kondo (OK) models for subsurface shales, and compare commonly used mono- and multilayer adsorption models (e.g., Langmuir, supercritical Dubinin-Radushkevich (SDR), supercritical BET (SBET), and simplified OK (OKs) models) with recently proposed pressure-dependent adsorption densities to develop a practical and reliable methodology that can be used in the supercritical state, typical for subsurface black shale conditions. Three independent data sets were used for nitrogen and methane adsorption isotherms at different temperatures. We demonstrate that adsorption predicted by the SDR model is comparable or lower than that predicted by the SBET model, but higher than the amounts predicted by Langmuir and OK models. The nitrogen BET method tends to underestimate the accessible SSA for methane. Measurement of isosteric heat of adsorption is suggested instead of the experimental fitting method, due to the significant difference between the calculated results by two commonly used methods. Experimental fitting and simulation methods are also briefly reviewed to guide future research on shale gas adsorption.

Original languageEnglish
Article number119454
JournalFuel
Volume287
DOIs
StatePublished - Mar 1 2021

Funding

We acknowledge the financial support of Center for Energy Research, Training, and Innovation (CERTAIN Seed Grant), Friends of Orton Hall (FOH) Grants, AAPG Grant-in-Aid, Ohio Department of Natural Resources, Division of Geological Survey Grant (ONDR Rock Grant), Alumni Grants for Graduate Research and Scholarship at The Ohio State University, American Chemical Society Petroleum Research Funding. This work was supported in part by The Ohio State University Office of Energy and Environment. Special thanks are given to the Shaanxi Yanchang Petroleum (Group) Co. Ltd. for providing drilling cores used in our previous work. Contributions to previous measurements of experimental data and manuscript preparation by G.R. were supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, Chemical Sciences, Geosciences and Biosciences Division. We acknowledge the financial support of Center for Energy Research, Training, and Innovation (CERTAIN Seed Grant), Friends of Orton Hall (FOH) Grants, AAPG Grant-in-Aid, Ohio Department of Natural Resources, Division of Geological Survey Grant (ONDR Rock Grant), Alumni Grants for Graduate Research and Scholarship at The Ohio State University, American Chemical Society Petroleum Research Funding. This work was supported in part by The Ohio State University Office of Energy and Environment. Special thanks are given to the Shaanxi Yanchang Petroleum (Group) Co., Ltd. for providing drilling cores used in our previous work. Contributions to previous measurements of experimental data and manuscript preparation by G.R. were supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, Chemical Sciences, Geosciences and Biosciences Division.

FundersFunder number
Division of Geological Survey
Friends of Orton Hall
Office of Basic Energy Sciences
Ohio Department of Natural Resources
Ohio State University Office of Energy and Environment
Shaanxi Yanchang Petroleum (Group) Co. Ltd.
U.S. Department of Energy
Department of Natural Resources
Office of Science
Basic Energy Sciences
American Chemical Society Petroleum Research Fund
Ohio State University
American Association of Petroleum Geologists
Chemical Sciences, Geosciences, and Biosciences Division

    Keywords

    • Langmuir
    • Ono-Kondo
    • Shale gas
    • Supercritical BET
    • Supercritical Dubinin-Radushkevich
    • Supercritical adsorption

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