(25b) Molecular Modeling of Structure and Transport of CO2 In Organic-Based Systems

CO₂ capture and sequestration is considered a primary, large-scale option for atmospheric CO₂ concentration stabilization. The aim of the current work is to fundamentally understand the molecular processes relevant to enhanced natural gas recovery from coal and gas shales using CO₂ with potential carbon storage. Molecular simulations have been carried out to model the organic matrix comprising coal and gas shales’ microfracture and related pore networks that serve as mechanisms of gas transport. To study these phenomena, molecular dynamics simulations have been carried out to investigate the transport properties of pure carbon dioxide, methane and nitrogen as well as binary mixtures consisting of nitrogen and carbon dioxide and also methane and carbon dioxide. The carbon models are represented by a three-dimensional pore space, generated atomistically by Voronoi tessellation of the space, using tens of thousands of atoms. We use non-equilibrium molecular dynamics simulations with an external chemical potential or pressure gradient imposed on the system. Extensive simulations are carried out to study the effect of the pore structure including defected graphite and also microfractures. The permeability results are compared with available experimental data. These fundamental studies will lead to an understanding of the mechanism associated gas transport in these confined carbon spaces and could potentially lead to the enhanced recovery of natural gas with the potential for CO₂ storage in coalbeds and gas shales.