Adsorption-Induced Deformation of Microporous Materials: Coal Swelling Induced by CO₂–CH₄ Competitive Adsorption

Abstract

Carbon dioxide injection in coal seams is known to improve the methane production of the coal seam, while ensuring a safe and long-term carbon sequestration. This improvement is due to the preferential adsorption of CO(2) in coal with respect to CH(4): an injection of CO(2) thus results in a desorption of CH(4). However, this preferential adsorption is also known to cause a differential swelling of coal, which results in a significant decrease in the reservoir permeability during the injection process. Recent studies have shown that adsorption in coal micropores (few angströms in size) is the main cause of the swelling. In this work, we focus on the competitive adsorption behavior of CO(2) and CH(4) in micropores. We perform molecular simulations of adsorption with a realistic atomistic model for coal. The competitive adsorption is studied at various temperatures and pressures representative of those in geological reservoirs. With the help of a poromechanical model, we then quantify the subsequent differential swelling induced by the computed adsorption behaviors. The differential swelling is almost insensitive to the geological temperatures and pressures considered here and is proportional to the CO(2) mole fraction in the coal.

Adsorption-induced deformation of nanoporous materials—A review

“…Swelling results in the narrowing and even closing of the macropores and fractures that are providing the permeability of the coal formation, complicating the ECBMR operation. Substantial amounts of work have been done in an attempt to develop models for adsorption-induced coal swelling in the last decade, 158,[190][191][192][193][194][195][196] yet it still remains a challenging problem. Moreover, there is a concern that adsorption-induced deformation may affect the extraction of shale gas in a way similar to ECBMR.…”

Molecular simulation studies of hydrocarbon and carbon dioxide adsorption on coal

“…Understanding the mechanism of CH 4 , C 2 H 6 , and CO 2 sorption on coal is a key factor for CO 2 storage and hydrocarbons recovery. Sorption of gases in coal has been studied for decades (Bae and Bhatia 2006;Billemont et al 2011Billemont et al , 2013Brochard et al 2012aBrochard et al , 2012bBusch and Gensterblum 2011;Busch et al 2003Busch et al , 2004Day et al 2008;Fitzgerald et al 2005;Gensterblum et al 2014;Goodman et al 2007;Krooss et al 2002;Li et al 2010;Ottiger et al 2008;Pini et al 2009Pini et al , 2010. Theoretical models have been developed and improved to study gas sorption on coal by several authors (Connell et al 2010;Lu and Connell 2007;Lu et al 2008;Pan and Connell 2007, 2012Sakurovs et al 2007; Vandamme et al 2010).…”

Adsorption-induced permeability change of porous material: a micromechanical model and its applications

“…(1) and (2), the data of the state equation of gas observed by the conventional experimental manner should be used, which are discussed in Sect. 4.…”

“…To consider such surface energy induced by adsorption, the corresponding constitutive model was proposed by Coussy [8] and Vandamme et al [39], respectively. Recently, from the free energy balance of the open system composed of the solid skeleton and the interstitial fluid, this model was further extended to a general form, which is valid not only to characterize the adsorption effect of microporous material, but also to describe the adsorption response of macroporous material [3,4]. Although the model is derived from very perspectives, it requires the help of molecular simulations for the theory to be applicable.…”