Shale gas storage in kerogen nanopores with surface heterogeneities

Recent advances in drilling and well stimulation technologies have led to rapid development of shale formations as an important natural gas resource. However a comprehensive understanding of the source rock geochemistry is currently needed in order to identify key factors in resource shale hydrocarbon assessment and production forecasting. Previous works indicated that significant amount of methane is stored in kerogen in adsorbed state. Adsorption is controlled by surface area and surface properties of the kerogen nanopore walls. In this paper using molecular simulations we investigate the influence of surface chemistry and heterogeneity on methane storage in model kerogen pores. The results show excess amount of methane due to nanopore confinement effect, which is found to be most pronounced under the subsurface conditions when the reservoir pore pressure is in the range of 1000-5000 psi. Among the investigated surface heterogeneities, nitrogen-doped graphene surfaces are the most influential on methane storage. Doping affects strongly the Langmuir parameters related to the adsorption capacity. These results indicate that kerogen maturation and the associated changes in its composition has the potential to impact gas storage in resource shale formations. The work gives new insights into the potential impact of the surface chemistry on natural gas storage in kerogen and emphasizes the significance of source rock geochemistry.