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Title: Methane Diffusion and Adsorption in Shale Rocks: A Numerical Study Using the Dusty Gas Model in TOUGH2/EOS7C-ECBM

Abstract

Gas production from shale gas reservoirs plays a significant role in satisfying increasing energy demands. Compared with conventional sandstone and carbonate reservoirs, shale gas reservoirs are characterized by extremely low porosity, ultra-low permeability and high clay content. Slip flow, diffusion, adsorption and desorption are the primary gas transport processes in shale matrix, while Darcy flow is restricted to fractures. Understanding methane diffusion and adsorption, and gas flow and equilibrium in the low-permeability matrix of shale is crucial for shale formation evaluation and for predicting gas production. Modeling of diffusion in low-permeability shale rocks requires use of the Dusty gas model (DGM) rather than Fick’s law. The DGM is incorporated in the TOUGH2 module EOS7C-ECBM, a modified version of EOS7C that simulates multicomponent gas mixture transport in porous media. Also included in EOS7C-ECBM is the extended Langmuir model for adsorption and desorption of gases. In this study, a column shale model was constructed to simulate methane diffusion and adsorption through shale rocks. The process of binary CH 4- N 2 diffusion and adsorption was analyzed. A sensitivity study was performed to investigate the effects of pressure, temperature and permeability on diffusion and adsorption in shale rocks. The results show that methanemore » gas diffusion and adsorption in shale is a slow process of dynamic equilibrium, which can be illustrated by the slope of a curve in CH4mass variation. The amount of adsorption increases with the pressure increase at the low pressure, and the mass change by gas diffusion will decrease due to the decrease in the compressibility factor of the gas. With the elevated temperature, the gas molecules move faster and then the greater gas diffusion rates make the process duration shorter. The gas diffusion rate decreases with the permeability decrease, and there is a limit of gas diffusion if the permeability is less than 1.0×10 -15 m 2. In conclusion, the results can provide insights for a better understanding of methane diffusion and adsorption in the shale rocks so as to optimize gas production performance of shale gas reservoirs.« less

Authors:
ORCiD logo [1];  [2];  [2];  [2];  [2];  [2]
  1. Chinese Academy of Sciences (CAS), Beijing (China). Key Lab. for Mechanics in Fluid Solid Coupling Systems, Inst. of Mechanics; Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Energy Geosciences Division; Chinese Academy of Sciences (CAS), Langfang (China). Inst. of Porous Flow and Fluid Mechanics
  2. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Energy Geosciences Division
Publication Date:
Research Org.:
Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
Sponsoring Org.:
USDOE Office of Science (SC)
OSTI Identifier:
1460342
Grant/Contract Number:  
AC02-05CH11231; ESD14085
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Transport in Porous Media
Additional Journal Information:
Journal Volume: 123; Journal Issue: 3; Journal ID: ISSN 0169-3913
Publisher:
Springer
Country of Publication:
United States
Language:
English
Subject:
04 OIL SHALES AND TAR SANDS

Citation Formats

Shen, Weijun, Zheng, Liange, Oldenburg, Curtis M., Cihan, Abdullah, Wan, Jiamin, and Tokunaga, Tetsu K.. Methane Diffusion and Adsorption in Shale Rocks: A Numerical Study Using the Dusty Gas Model in TOUGH2/EOS7C-ECBM. United States: N. p., 2018. Web. doi:10.1007/s11242-017-0985-y.
Shen, Weijun, Zheng, Liange, Oldenburg, Curtis M., Cihan, Abdullah, Wan, Jiamin, & Tokunaga, Tetsu K.. Methane Diffusion and Adsorption in Shale Rocks: A Numerical Study Using the Dusty Gas Model in TOUGH2/EOS7C-ECBM. United States. doi:10.1007/s11242-017-0985-y.
Shen, Weijun, Zheng, Liange, Oldenburg, Curtis M., Cihan, Abdullah, Wan, Jiamin, and Tokunaga, Tetsu K.. Wed . "Methane Diffusion and Adsorption in Shale Rocks: A Numerical Study Using the Dusty Gas Model in TOUGH2/EOS7C-ECBM". United States. doi:10.1007/s11242-017-0985-y. https://www.osti.gov/servlets/purl/1460342.
@article{osti_1460342,
title = {Methane Diffusion and Adsorption in Shale Rocks: A Numerical Study Using the Dusty Gas Model in TOUGH2/EOS7C-ECBM},
author = {Shen, Weijun and Zheng, Liange and Oldenburg, Curtis M. and Cihan, Abdullah and Wan, Jiamin and Tokunaga, Tetsu K.},
abstractNote = {Gas production from shale gas reservoirs plays a significant role in satisfying increasing energy demands. Compared with conventional sandstone and carbonate reservoirs, shale gas reservoirs are characterized by extremely low porosity, ultra-low permeability and high clay content. Slip flow, diffusion, adsorption and desorption are the primary gas transport processes in shale matrix, while Darcy flow is restricted to fractures. Understanding methane diffusion and adsorption, and gas flow and equilibrium in the low-permeability matrix of shale is crucial for shale formation evaluation and for predicting gas production. Modeling of diffusion in low-permeability shale rocks requires use of the Dusty gas model (DGM) rather than Fick’s law. The DGM is incorporated in the TOUGH2 module EOS7C-ECBM, a modified version of EOS7C that simulates multicomponent gas mixture transport in porous media. Also included in EOS7C-ECBM is the extended Langmuir model for adsorption and desorption of gases. In this study, a column shale model was constructed to simulate methane diffusion and adsorption through shale rocks. The process of binary CH4- N2 diffusion and adsorption was analyzed. A sensitivity study was performed to investigate the effects of pressure, temperature and permeability on diffusion and adsorption in shale rocks. The results show that methane gas diffusion and adsorption in shale is a slow process of dynamic equilibrium, which can be illustrated by the slope of a curve in CH4mass variation. The amount of adsorption increases with the pressure increase at the low pressure, and the mass change by gas diffusion will decrease due to the decrease in the compressibility factor of the gas. With the elevated temperature, the gas molecules move faster and then the greater gas diffusion rates make the process duration shorter. The gas diffusion rate decreases with the permeability decrease, and there is a limit of gas diffusion if the permeability is less than 1.0×10-15 m2. In conclusion, the results can provide insights for a better understanding of methane diffusion and adsorption in the shale rocks so as to optimize gas production performance of shale gas reservoirs.},
doi = {10.1007/s11242-017-0985-y},
journal = {Transport in Porous Media},
number = 3,
volume = 123,
place = {United States},
year = {Wed Jan 03 00:00:00 EST 2018},
month = {Wed Jan 03 00:00:00 EST 2018}
}

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Works referenced in this record:

TOUGH2 User's Guide Version 2
report, November 1999

  • Pruess, K.; Oldenburg, C.M.; Moridis, G.J.
  • LBNL--43134
  • DOI: 10.2172/751729