{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2025,11,3]],"date-time":"2025-11-03T09:13:35Z","timestamp":1762161215585,"version":"3.38.0"},"reference-count":40,"publisher":"SAGE Publications","issue":"4","license":[{"start":{"date-parts":[[2016,4,12]],"date-time":"2016-04-12T00:00:00Z","timestamp":1460419200000},"content-version":"tdm","delay-in-days":0,"URL":"https:\/\/journals.sagepub.com\/page\/policies\/text-and-data-mining-license"}],"content-domain":{"domain":["journals.sagepub.com"],"crossmark-restriction":true},"short-container-title":["Energy Exploration &amp; Exploitation"],"published-print":{"date-parts":[[2016,7]]},"abstract":"<jats:p> The study of the gas diffusion process has a main role in both coalbed methane (CBM) production and CO<jats:sub>2<\/jats:sub> injection in geological sequestration projects. The accurate determination of gas diffusion coefficients in unconventional reservoirs such as coal seams requires a consistent mathematical approach. The study of the gas diffusion process in coal seams was carried out using sorption isotherms. The Langmuir model for individual gases and the extended Langmuir model for multicomponent gas mixtures were applied to fit sorption isotherm data. \u201cGas content derivative data\u201d and \u201cgas content changes\u201d emerged as crucial mathematical parameters to accurately study the gas diffusion process. The main goal of this paper is to define the degree of interaction between the gas content derivative data and the gas diffusion process. Experiments were performed on three samples selected from two different coals, which were submitted to three different gas compositions, viz 99.999% CH<jats:sub>4<\/jats:sub>; 99.999% CO<jats:sub>2<\/jats:sub>; and a gas mixture containing 74.99% CH<jats:sub>4<\/jats:sub>\u2009+\u200919.99% CO<jats:sub>2<\/jats:sub>\u2009+\u20095.02% N<jats:sub>2<\/jats:sub>, at 35\u2103, and at pressures ranging from 0 up to 50\u2009bar. Experimental results obtained from the three samples indicate that during adsorption\/desorption processes, the diffusion coefficients increase and the gas content changes decrease when the pressure decreases, due to the sample saturation degrees and to the kinetic mechanisms increase. Additionally, the \u201cgas content derivative data\u201d scattering is slightly lower during the desorption process than during the adsorption process. These behaviours are clearly identified when using methane, but are even more evident when using CO<jats:sub>2<\/jats:sub> and the gas mixture, due to the CO<jats:sub>2<\/jats:sub> interaction with coal porous structure, which induces a considerable resistance to CO<jats:sub>2<\/jats:sub> release. The results show that sample B (CH<jats:sub>4<\/jats:sub>\u2009+\u2009CO<jats:sub>2<\/jats:sub>\u2009+\u2009N<jats:sub>2<\/jats:sub>) displays higher diffusion coefficient values (this behaviour is mainly related to the presence of N<jats:sub>2<\/jats:sub>) than sample C (CH<jats:sub>4<\/jats:sub>) and than sample A (CO<jats:sub>2<\/jats:sub>). <\/jats:p>","DOI":"10.1177\/0144598716643629","type":"journal-article","created":{"date-parts":[[2016,4,13]],"date-time":"2016-04-13T01:12:48Z","timestamp":1460509968000},"page":"606-620","update-policy":"https:\/\/doi.org\/10.1177\/sage-journals-update-policy","source":"Crossref","is-referenced-by-count":5,"title":["Gas content derivative data versus diffusion coefficient"],"prefix":"10.1177","volume":"34","author":[{"given":"Cristina Fernanda Alves","family":"Rodrigues","sequence":"first","affiliation":[{"name":"Fernando Pessoa University (UFP), UFP Energy, Environment and Health Research Unit (FP-ENAS), Energy, Environment and Environmental & Public Health Research Laboratories (3ERL), Pra\u00e7a de 9 de Abril 349, 4249-004 Oporto, Portugal"}]},{"given":"Maria Alzira Pimenta","family":"Dinis","sequence":"additional","affiliation":[{"name":"Fernando Pessoa University (UFP), UFP Energy, Environment and Health Research Unit (FP-ENAS), Energy, Environment and Environmental & Public Health Research Laboratories (3ERL), Pra\u00e7a de 9 de Abril 349, 4249-004 Oporto, Portugal"}]},{"given":"Manuel Jo\u00e3o","family":"Lemos de Sousa","sequence":"additional","affiliation":[{"name":"Fernando Pessoa University (UFP), UFP Energy, Environment and Health Research Unit (FP-ENAS), Energy, Environment and Environmental & Public Health Research Laboratories (3ERL), Pra\u00e7a de 9 de Abril 349, 4249-004 Oporto, Portugal"},{"name":"Academia das Ci\u00eancias de Lisboa, Rua da Academia das Ci\u00eancias 19, 1249-122 Lisbon, Portugal"}]}],"member":"179","published-online":{"date-parts":[[2016,4,12]]},"reference":[{"key":"bibr1-0144598716643629","unstructured":"ASTM D1412-04 (2005) Standard test method for equilibrium moisture of coal at 96 to 97 percent relative humidity and 30\u2103. 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