About This Item

This article has been peer-reviewed and accepted for publication in a future issue of the AAPG Bulletin. This abstract and associated PDF document are based on the authors' accepted "as is" manuscript.

Editorial Policy for Ahead of Print

Cite This Item

Display Citation

Share This Item

The AAPG/Datapages Combined Publications Database

AAPG Bulletin

Visit Publisher's Website  

Ahead of Print Abstract

AAPG Bulletin, Preliminary version published online Ahead of Print 1 August 2023.

Copyright © 2023. The American Association of Petroleum Geologists. All rights reserved.


Effects of light hydrocarbons and extractable organic matter on the methane sorption capacity of shales

Qian Zhang12 , Reinhard Fink1 , Bernhard M. Krooss1 , Zhijun Jin2 , Rukai Zhu3 , Zhazha Hu1 , Garri Gaus1 , and Ralf Littke1

1 Institute of Geology and Geochemistry of Petroleum and Coal, Energy and Mineral Resources Group (EMR), RWTH Aachen University, Aachen, Germany
2 Institute of Energy, School of Earth and Space Sciences, Peking University, Beijing, China
3 PetroChina Research Institute of Petroleum Exploration and Development, Beijing, China

Ahead of Print Abstract

High-pressure methane (CH4) sorption measurements at 30°C and up to 20 MPa have been conducted on four carbonaceous shales with Total Organic Carbon (TOC) contents ranging from 8.52 to 11.73 wt.% and different maturities (0.53 to 1.45% vitrinite reflectance (VRr)). Excess sorption isotherms were measured on all four samples in the “dry”, “solvent-extracted”, “hexane-equilibrated” and “moisture-equilibrated” states. The isotherms of all samples, irrespective of thermal maturity, showed consistent effects of extraction, pre-adsorbed hexane, and moisture on methane sorption capacity. Removal of bitumen by solvent extraction generally increases the methane sorption capacity of the shales (at 1 MPa) by up to 63% compared to the dry state, most likely due to enhancing the accessibility of sorption sites. Moisture consistently reduces methane sorption capacity by about 23 to 48% as compared to the dry (unextracted) state. The effect of pre-adsorbed hexane on methane sorption capacity is strongly pressure-dependent: At low pressures its influence is negative and at high pressures positive. The significant increase of sorption capacity at high pressures is attributed to the almost linear increase of methane solubility in hexane with pressure while methane adsorption on the organic and mineral surfaces reaches saturation. The pre-adsorbed hexane reduces methane sorption capacity by about 20 to 40% if solubility effects are excluded. In view of these findings, the methane adsorption capacity of shales at the “wet gas” maturity level should be reconsidered. Our observations contribute to a better understanding of natural gas occurrence and producibility in liquid-bearing unconventional petroleum systems and a more accurate estimation of gas-in-place of shale gas reservoirs.

Pay-Per-View Purchase Options

The article is available through a document delivery service. Explain these Purchase Options.

Watermarked PDF Document: $14
Open PDF Document: $24

AAPG Member?

Please login with your Member username and password.

Members of AAPG receive access to the full AAPG Bulletin Archives as part of their membership. For more information, contact the AAPG Membership Department at [email protected].

Please cite this AAPG Bulletin Ahead of Print article as:

Qian Zhang , Reinhard Fink , Bernhard M. Krooss , Zhijun Jin , Rukai Zhu , Zhazha Hu , Garri Gaus , Ralf Littke: Effects of light hydrocarbons and extractable organic matter on the methane sorption capacity of shales, (in press; preliminary version published online Ahead of Print 01 August 2023: AAPG Bulletin, DOI:10.1306/05302322009.