Phase states of methane in fossil coals

• Published in: Solid state communications Vol. 130; no. 10; pp. 669 - 673
• Main Authors: Alexeev, A.D., Vasylenko, T.A., Ul'yanova, E.V.
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 01.06.2004; Elsevier
• Subjects: A. Coal; A. Methane; Crystalline rocks; E. Nuclear magnetic resonance; Earth sciences; Earth, ocean, space; Exact sciences and technology; External geophysics; Geophysics. Techniques, methods, instrumentation and models; E. Nuclear magnetic resonance; A. Methane; 76.60.Jx; 76.60.−k; A. Coal; molecular structure; carbonaceous rocks; sedimentary rocks; k; 76.60.Jx A. Coal; A. Methane; E. Nuclear magnetic resonance; coal; 76.60; nuclear magnetic resonance
• ISSN: 0038-1098; 1879-2766
• DOI: 10.1016/j.ssc.2004.03.034

NMR measurements have revealed that methane can exist in coal samples in the state of solid solution rather than only adsorbed gas, opening new ways to prevention of gas dynamic accidents in underground coal mines and true estimation of coalbed methane resources. Understanding molecular structure of coal constituents and forms of methane occurrence in coal is the only way of extracting safely either coal or methane. We had studied nuclear magnetic resonance lines in various coals at room or low temperatures and have found that there exist three species of methane molecules differing in molecular mobility. Based on estimated diffusion parameters, these species were attributed to free methane, adsorbed methane, and solid solution of methane in crystalline coal substance. While first two phases are well known and can be analyzed by many different techniques, the last one hardly can be studied by methods other than NMR, resulting in inadequate estimations of methane resources.