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Combining molecular simulation and experiment to understand the effect of moisture on methane adsorption in kerogens

Li, Wei; Stevens, Lee A.; Zhang, Bo; Zheng, Dingye; Snape, Colin E.

Authors

WEI LI WEI.LI7@NOTTINGHAM.AC.UK
Research Fellow

LEE STEVENS LEE.STEVENS@NOTTINGHAM.AC.UK
Senior Research Fellow

Bo Zhang

Dingye Zheng

COLIN SNAPE COLIN.SNAPE@NOTTINGHAM.AC.UK
Professor of Chemical Technology & Chemical Eng



Abstract

There is a limited understanding of the critical impact moisture has on shale gas resource estimation by affecting gas adsorption and pore structure. Laboratory experiments on dry and 95% relative humidity (R.H.) isolated kerogens are combined with Grand Canonical Monte Carlo (GCMC) and Molecular Dynamic (MD) simulations for kerogen models, including matrix and slits (0.5, 1.0, 1.5, and 2.0 nm) with a range of moisture contents (0–42 wt% on a total organic carbon content (TOC) basis) to better understand how moisture impacts methane adsorption. Higher methane adsorption capacities (Qm) and micropore volumes (Vmicro) are observed for simulated kerogens since all pores in GCMC are accessible. Moisture has a negative effect on Qm, displaying ‘rapid’, ‘gentle’, and ‘slow’ stages with increasing moisture in simulation. Reductions in Qm (61–75%) and Vmicro (88–93%) are obtained for isolated kerogens containing moisture of 38–70 wt% TOC with up to 56% of the moisture in micropores. The same Qm and Vmicro reductions can be reached for the simulated kerogens with moisture contents of 4–24 wt% TOC for matrix and slits. The relative coordination number (Cr) from MD simulation indicates water has a stronger affinity than methane for all functional groups with preferred sorption sites like carboxyl (COOH) under reservoir conditions. The microporosity controls condensed water cluster size. Water adsorbed in ultra-micropores (<0.7 nm) leads to ‘rapid’ reduction, the ‘gentle’ Qm reduction stage arises from water condensing, and filling of remaining pores at the highest moisture is related to the ‘slow’ Qm reduction stage. Therefore, water reduces the methane adsorption capacity of kerogen mainly by occupying and blocking the pore volume rather than competing directly with methane for sorption sites.

Citation

Li, W., Stevens, L. A., Zhang, B., Zheng, D., & Snape, C. E. (2023). Combining molecular simulation and experiment to understand the effect of moisture on methane adsorption in kerogens. Chemical Engineering Journal, 454, 139942. https://doi.org/10.1016/j.cej.2022.139942

Journal Article Type Article
Acceptance Date Oct 17, 2022
Online Publication Date Nov 2, 2022
Publication Date Feb 15, 2023
Deposit Date Oct 12, 2023
Publicly Available Date Nov 2, 2023
Journal Chemical Engineering Journal
Print ISSN 1385-8947
Electronic ISSN 1873-5606
Publisher Elsevier
Peer Reviewed Peer Reviewed
Volume 454
Pages 139942
DOI https://doi.org/10.1016/j.cej.2022.139942
Keywords Industrial and Manufacturing Engineering; General Chemical Engineering; Environmental Chemistry; General Chemistry
Public URL https://nottingham-repository.worktribe.com/output/25811120

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