Title: Effect of gas compressibility factor estimation in coal sorption isotherms accuracy

Authors: C.F.A. Rodrigues; J.M. Machado Da Silva; M.A.P. Dinis; M.J. Lemos De Sousa

Addresses: UFP Energy, Environment and Health Research Unit (FP-ENAS), Fernando Pessoa University (UFP), Praça de 9 de Abril 349, 4249-004 Porto, Portugal ' Institute of Nanoscience and Nanotechnology (IN), Rua Alves Redol, 1000-029 Lisboa, Portugal ' UFP Energy, Environment and Health Research Unit (FP-ENAS), Fernando Pessoa University (UFP), Praça de 9 de Abril 349, 4249-004 Porto, Portugal ' UFP Energy, Environment and Health Research Unit (FP-ENAS), Fernando Pessoa University (UFP), Praça de 9 de Abril 349, 4249-004 Porto, Portugal; Academia das Ciências de Lisboa, Rua da Academia das Ciências, 19, 1249-122 Lisboa, Portugal

Abstract: Compressibility factor (CF) is a key parameter in gas industry, regarding gas flow and storage in a gas reservoir. This study highlights the necessity to accurately estimate CF, affecting reservoir sorption capacity determination. The effect of the CF of N2, CH4 and CO2 in the coal porous structure was studied. Sorption isotherms showed no significant hysteresis regarding N2, due to gas inert behaviour. CH4 has a higher CF slope and the hysteresis behaviour is stronger than in N2. CO2 has no linear CF behaviour and besides relevant hysteresis, a distinct general trend between both curve shapes was identified, and the CO2 desorption curve intercepted the CO2 adsorption curve at 30 × 105 Pa. This is due to CO2 retention on coal porous structure, thanks to the great affinity between CO2 and the organic microporous structure, to pressures up to 6.9 × 105 Pa. The gas mixture showed a significant hysteresis due to its composition. [Received: 28 April, 2016; Accepted: 11 May, 2017]

Keywords: coalbed methane; gas compressibility factor; isotherm; sorption.

DOI: 10.1504/IJOGCT.2018.094544

International Journal of Oil, Gas and Coal Technology, 2018 Vol.19 No.2, pp.230 - 247

Available online: 22 Aug 2018 *

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