Formation of Methane Clathrate Hydrates in Coal Moisture: Implications for Coalbed Methane Resources and Reservoir Pressures

Abstract

Access and use of this website and the material on it are subject to the Terms and Conditions set forth at NRC Publications Record / Notice d'Archives des publications de CNRC:http://nparc.cisti-icist.nrc-cnrc.gc.ca/npsi/ctrl?action=rtdoc&an=21277454&lang=en http://nparc.cisti-icist.nrc-cnrc.gc.ca/npsi/ctrl?action=rtdoc&an=21277454&lang=fr READ THESE TERMS AND CONDITIONS CAREFULLY BEFORE USING THIS WEBSITE.http://nparc.cisti-icist.nrc-cnrc.gc.ca/npsi/jsp/nparc_cp.jsp?lang=en Vous avez des questions? Nous pouvons vous aider. Pour communiquer directement avec un auteur, consultez la première page de la revue dans laquelle son article a été publié afin de trouver ses coordonnées. Si vous n'arrivez pas à les repérer, communiquez avec nous à PublicationsArchive-ArchivesPublications@nrc-cnrc.gc.ca. Questions?Contact the NRC Publications Archive team at PublicationsArchive-ArchivesPublications@nrc-cnrc.gc.ca. If you wish to email the authors directly, please see the first page of the publication for their contact information. NRC Publications Archive Archives des publications du CNRCThis publication could be one of several versions: author's original, accepted manuscript or the publisher's version. / La version de cette publication peut être l'une des suivantes : la version prépublication de l'auteur, la version acceptée du manuscrit ou la version de l'éditeur. For the publisher's version, please access the DOI link below./ Pour consulter la version de l'éditeur, utilisez le lien DOI ci-dessous.http://doi.org/10.1021/acs.energyfuels.5b01922 Energy and Fuels, 30, 1, pp. 88-97, 2015-12-04 Formation of ABSTRACT: Adsorption, X-ray diffraction, and nuclear magnetic resonance analysis of subbituminous to high-volatile bituminous coal at in situ moisture content, low temperatures, and moderate pressures demonstrate that a significant proportion of the inherent moisture (nonmobile water) is available to form methane clathrate hydrates. These results have implications for coal gas resources and reservoir pressures in current areas of permafrost and the much larger regions that were glaciated during the Pleistocene. Methane adsorption tests indicate the clathrates form comparatively rapidly in coal micro-and mesopores from an immobile water phase, at lower pressures than those formed in macroporous materials. At successively higher experimental pressures, hydrates nucleate and grow rapidly on the scale of minutes to hours, until an "apparent" equilibrium pressure is reached. The onset of hydrate formation at 0°C is at about 3.25 MPa for a Tarn coal with 33% moisture and at slightly higher pressures for the other coals with lower inherent moisture. The amount of gas consumed in hydrate formation, in excess of that attributed to sorption, is 11.6 cm 3 /g coal for the Tarn coal (Alaska) with 33% moisture, 8.15 cm 3 /g coal for a Dietz coal (Wyoming) with 22% moisture, and 1.85 cm 3 /g coal for a Texas coal with about 8% moisture. On a volume of gas (STP) per volume of water basis at 8 MPa, the Tarn and Dietz coal have similar ...

Methane Hydrate in Confined Spaces: An Alternative Storage System

“…determined by 13 C NMR the occupancy of 90 % of the small cages in coal moisture, yielding a stoichiometry of ca. CH 4 ⋅6H 2 O. The observed broad signal at −4.8 ppm (short T2) could also be assigned to methane dissolved in water, which hints towards weak interaction of these species with the pore wall.…”

“…Experimental hydration number was calculated and reported in several works for natural and synthetic sI methane hydrate, either in bulk or confined conditions. The reported values range from about 5.8 to 6.3 when full large cavity occupancy is assumed ,…”

“…It can be analyzed equally to Raman due to the presence of a cage‐dependent chemical shift for enclathrated methane . The two signals at −4.2 and −6.7 ppm are typical of methane in the small and large cages, respectively in sI hydrate . The technique provides structural evidence not only for natural methane hydrate but also synthetic methane hydrate in bulk or in confined space.…”

Effect of the Hydrate Saturation of the Pores of Coal Bed on the Gradient of Gas Pressure and the Rise of Outburst Danger

“…Gas hydrates are one of the possible forms in which methane is present in coal beds [12][13][14][15]. Up to 160 volumes of gas (reduced to the normal conditions) are released from one volume of the hydrate.…”

Characteristics of in situ stress and its influence on coalbed methane development: A case study in the eastern part of the southern Junggar Basin, NW China

“…22,23 The P o reflects the flowing capacity of methane gas and formation water from the porefracture system to the wellbore, and it has great significance for the CBM development effect. 53 The P o is closely related to the current in situ stress regime, and the latter can affect the former by exerting confining pressure on the fluid of the pore-fracture system. 54 In general, coal reservoirs usually have greater P 0 and G 0 values within a compressive stress regime, whereas smaller P 0 and G 0 values existed in a tensional stress regime.…”