Gas storage in model kerogen pores with surface heterogeneities
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abstract
Copyright 2016, Society of Petroleum Engineers. Experimental techniques have limited applicability in investigating the nature of fluid storage in kerogen pores under subsurface conditions. In this paper we present a computational chemistry approach and present new numerical results on supercritical methane storage influenced by nano-scale pore confinement and pore wall surface heterogeneities. The results show that gas amount stored in the pore is not strongly correlated with nano-pore confinement. Measured excess amount due to confinement is most pronounced at pore pressure in the range of 1,000-5,000 psi. The pore wall surface heterogeneities have the potential to impact storage depending on the type and level of heterogeneities. Among the investigated heterogeneities, nitrogen-doping at the pore walls is found to be the most influential. The adsorbed amount decreased up to 63% and the excess amount increased up to 37%, with the nitrogen-doped pore wall surfaces. The net storage is inversely correlated with the concentration of the nitrogen atoms. The results indicate that kerogen maturation and the associated changes in its composition has the potential to impact gas storage and transport in resource shale reservoirs. The work gives insight into the potential impact of the surface effects on natural gas storage in kerogen and emphasizes the significance of knowledge on the source rock geochemistry.
