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Title: Differential retention and release of CO2 and CH4 in kerogen nanopores: Implications for gas extraction and carbon sequestration

Abstract

Methane (CH4) and carbon dioxide (CO2), the two major components generated from kerogen maturation, are stored dominantly in nanometer-sized pores in shale matrix as (1) a compressed gas, (2) an adsorbed surface species and/or (3) a species dissolved in pore water (H2O). In addition, supercritical CO2 has been proposed as a fracturing fluid for simultaneous enhanced oil/gas recovery (EOR) and carbon sequestration. A mechanistic understanding of CH4-CO2-H2O interactions in shale nanopores is critical for designing effective operational processes. Using molecular simulations, we show that kerogen preferentially retains CO2 over CH4 and that the majority of CO2 either generated during kerogen maturation or injected in EOR will remain trapped in the kerogen matrix. The trapped CO2 may be released only if the reservoir pressure drops below the supercritical CO2 pressure. When water is present in the kerogen matrix, it may block CH4 release. Furthermore, the addition of CO2 may enhance CH4 release because CO2 can diffuse through water and exchange for adsorbed methane in the kerogen nanopores.

Authors:
 [1];  [1];  [2];  [1]
  1. Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)
  2. Sandia National Lab. (SNL-NM), Carlsbad, NM (United States)
Publication Date:
Research Org.:
Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)
Sponsoring Org.:
USDOE National Nuclear Security Administration (NNSA)
OSTI Identifier:
1421764
Report Number(s):
SAND-2018-1044J
Journal ID: ISSN 0016-2361; 660339
Grant/Contract Number:  
AC04-94AL85000
Resource Type:
Accepted Manuscript
Journal Name:
Fuel
Additional Journal Information:
Journal Volume: 220; Journal Issue: C; Journal ID: ISSN 0016-2361
Publisher:
Elsevier
Country of Publication:
United States
Language:
English
Subject:
03 NATURAL GAS; Organic matter; Kerogen; Nanoscale transport; Shale gas; Carbon sequestration

Citation Formats

Ho, Tuan Anh, Wang, Yifeng, Xiong, Yongliang, and Criscenti, Louise J. Differential retention and release of CO2 and CH4 in kerogen nanopores: Implications for gas extraction and carbon sequestration. United States: N. p., 2018. Web. doi:10.1016/j.fuel.2018.01.106.
Ho, Tuan Anh, Wang, Yifeng, Xiong, Yongliang, & Criscenti, Louise J. Differential retention and release of CO2 and CH4 in kerogen nanopores: Implications for gas extraction and carbon sequestration. United States. doi:10.1016/j.fuel.2018.01.106.
Ho, Tuan Anh, Wang, Yifeng, Xiong, Yongliang, and Criscenti, Louise J. Tue . "Differential retention and release of CO2 and CH4 in kerogen nanopores: Implications for gas extraction and carbon sequestration". United States. doi:10.1016/j.fuel.2018.01.106. https://www.osti.gov/servlets/purl/1421764.
@article{osti_1421764,
title = {Differential retention and release of CO2 and CH4 in kerogen nanopores: Implications for gas extraction and carbon sequestration},
author = {Ho, Tuan Anh and Wang, Yifeng and Xiong, Yongliang and Criscenti, Louise J.},
abstractNote = {Methane (CH4) and carbon dioxide (CO2), the two major components generated from kerogen maturation, are stored dominantly in nanometer-sized pores in shale matrix as (1) a compressed gas, (2) an adsorbed surface species and/or (3) a species dissolved in pore water (H2O). In addition, supercritical CO2 has been proposed as a fracturing fluid for simultaneous enhanced oil/gas recovery (EOR) and carbon sequestration. A mechanistic understanding of CH4-CO2-H2O interactions in shale nanopores is critical for designing effective operational processes. Using molecular simulations, we show that kerogen preferentially retains CO2 over CH4 and that the majority of CO2 either generated during kerogen maturation or injected in EOR will remain trapped in the kerogen matrix. The trapped CO2 may be released only if the reservoir pressure drops below the supercritical CO2 pressure. When water is present in the kerogen matrix, it may block CH4 release. Furthermore, the addition of CO2 may enhance CH4 release because CO2 can diffuse through water and exchange for adsorbed methane in the kerogen nanopores.},
doi = {10.1016/j.fuel.2018.01.106},
journal = {Fuel},
number = C,
volume = 220,
place = {United States},
year = {2018},
month = {2}
}

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Cited by: 3 works
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Figures / Tables:

Fig. 1 Fig. 1: (A) Over-mature nanoporous kerogen structure. Red, blue, yellow, gray, and white spheres represent oxygen, nitrogen, sulfur, carbon, and hydrogen atoms, respectively. Pore-volume and kerogen interface is outlined in blue (i.e., surface side facing the pore volume) and in gray (i.e., surface side facing the kerogen atoms). (B) Cylindricalmore » carbon nanotube (CNT) connecting with a reservoir defined in between two flat graphene sheets. The pore size effect was investigated by changing CNT diameter from 0.814 nm to 1.085 nm. (C) Graphene slit-pore connecting with a reservoir. The pore shape effect was studied by comparing the results obtained for cylindrical pore (0.814 nm CNT – Fig. 1B) and for 0.814 nm graphene slit-pore (Fig. 1C). (D) Initial configuration to study the invasion of CO2 (cyan-red) into the methane (green)-filled CNT. (E) Simulation snapshot represents the water (red-white spheres) blocking at the opening of CNT filled with methane molecules (green spheres). The temperature is 338K for all simulations. Note that half of the CNT is removed to visualize the methane molecules inside. See SM for more simulation details regarding the number of molecules simulated and force field implemented. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)« less

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