Adsorption, selectivity, and phase behavior in organic nanopores for shale gas and oil development

Abstract

In a shale gas and oil reservoir, hydrocarbon fluids are stored in organic nanopores with sizes on the order of ∼1–100 nm. The adsorption, selectivity, and phase behavior of hydrocarbons in the nanopores are crucial for estimating the gas-in-place and predicting the productivity. In this study, to understand the characteristics of the phase behavior of multicomponent hydrocarbon systems in shale reservoirs, the phase behavior of a CH4/n-C4H10 binary mixture in graphite nanopores was investigated by Grand Canonical Monte Carlo (GCMC) molecular simulation. The method for determining the dew-point pressure and bubble-point pressure in the nanopores was explored. The condensation phenomenon was observed owing to the difference in the adsorption selectivities of the hydrocarbon molecules on the nanopore surfaces, and hence the dew-point pressure (and bubble-point pressure) of hydrocarbon mixtures in the nanopores significantly shifted. The GCMC simulations reproduced both the higher and lower bubble-point pressures in nanopores in previous studies. This work highlights the crucial role of the selectivity in the phase behavior of hydrocarbons in nanopores.

Keywords

• Shale gas and oil
• Nanopores
• Adsorption
• Selectivity
• Phase behavior
• Bubble point pressure