Competitive adsorption and reduced mobility: N-octane, CO₂ and H₂S in alumina and graphite pores

Abstract

Because gas injection into geological formations is a common technology deployed for enhanced oil recovery (EOR), it is important to understand at the molecular level the relations between competitive adsorption and fluid mobility at the single-pore level. To achieve such an understanding, we report here molecular dynamics simulation results to document structural and dynamical properties of n-octane confined in slit-shaped alumina and graphite pores in the presence of CO 2 or H 2 S. The substrates are chosen as proxy models for natural hydrophilic and hydrophobic substrates, respectively. It was found that CO 2 and H 2 S could displace n-octane from alumina but not from graphite surfaces. Analysis of the results demonstrates that more attractive n-octane -surface and weaker CO 2 /H 2 S -surface interactions in graphite compared to alumina are responsible for this observation. Regardless of pore type, the results suggest that adding CO 2 or H 2 S suppresses the diffusion of n-octane due to pore crowding. However, the mechanisms responsible for this observation are different, wherein preferential adsorption sites are available on the alumina surface for both CO 2 and H 2 S, but not on graphite. To contribute to designing advanced EOR technologies, possible molecular mechanisms are proposed to interpret the results.

Advances of nanotechnologies for hydraulic fracturing of coal seam gas reservoirs: potential applications and some limitations in Australia

“…Modelling studies are underway to better understand the molecular mechanisms responsible for these observations (e.g. Le et al 2015;Cole and Striolo 2019;Badmos et al 2020).…”

Interfacial and Confinement-Mediated Organization of Gas Hydrates, Water, Organic Fluids, and Nanoparticles for the Utilization of Subsurface Energy and Geological Resources

“…Calibrated insights into the fate of fluids in subsurface porous environments are needed. In this context, assessing the influence of pore sizes, shapes, geometries, surface chemistry on the structures, − dynamics, − ,− phase transitions, − rheology, − assembly, ,− and flow of confined fluids , is essential. Among these properties, there have been limited efforts to link the structures of confined fluids or assembly of molecules to the observed properties and the efficacy of fluid storage and recovery activities.…”