Differential retention and release of CO2 and CH4 in kerogen nanopores: Implications for gas extraction and carbon sequestration. (15th May 2018)

• Record Type: Journal Article
• Authors: Ho, Tuan Anh; Wang, Yifeng; Xiong, Yongliang; Criscenti, Louise J.
• Is Part Of: Fuel. Volume 220(2018)
• Page Start: 1
• Page End: 7
• Publication Date: 2018-05-15
• Subjects: Organic matter -- Kerogen -- Nanoscale transport -- Shale gas -- Carbon sequestration; Fuel -- Periodicals; Coal -- Periodicals; Coal; Fuel; Periodicals; 662.6
• DOI: 10.1016/j.fuel.2018.01.106
• Languages: English
• ISSNs: 0016-2361

Abstract

Graphical abstract: Highlights: Kerogen preferentially retains CO2 over CH4 . The CO2 may be released if the reservoir pressure drops below supercritical pressure. Upon contact with CO2, CH4 molecules in narrow cylindrical carbon pores are trapped. CO2 can diffuse through water and exchange for adsorbed methane in the carbon pores. 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 (H2 O). 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 -H2 O 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. However, the addition of CO2 may enhance CH4 release because CO2 can diffuse through water and exchange for adsorbed methane in the kerogen nanopores.