(178d) Deformation of Amorphous Nanoporous Carbons in the Process of Methane Displacement By Carbon Dioxide

The problem of predicting the adsorption-induced deformation of geological adsorbents has attracted much attention in the literature. Promising enhanced methane recovery techniques use injection of CO₂ into the geosorbents to encourage the desorption of methane and simultaneous adsorption of CO₂. This process offers higher yields of natural gas, reduced pollution by eliminating wastewater, and geological sequestration of CO₂, which displaces adsorbed methane. However, gas adsorption in geosorbents occurs in poroelastic nanoporous matrices, which deform significantly upon gas adsorption/desorption. Variability in the matrix volume can cause fluctuations in the surrounding macroporous cleat spaces and, respectively, in the reservoir permeability. Understanding the molecular-level mechanisms of adsorption-induced deformation is essential for developing safe, efficient natural gas harvesting and carbon sequestration techniques.

Previous molecular simulations studies have considered mixture adsorption in nanoporous carbons, but they are typically restricted to simplified structures that do not account for the nanoscale specifics of geosorbents. In this work, we perform simulations of competitive adsorption of mixtures of hydrocarbons and carbon dioxide at geologically relevant conditions on amorphous carbon structures, which are created by imitating the conditions of nanoporous carbon formation. We compare these results with simulations performed on ideal slit pore structures formed from perfect graphene sheets, which are typically used in simulations studies. We also calculate the stress and strain tensors in the amorphous carbon structures. This work will provide a new physical insight into adsorption deformation in geological adsorbents.