Molecular Simulation of Oil Mixture Adsorption Character in Shale System

Chemical kinetics theory and molecular dynamics simulation are used to study adsorption character of shale oil within nanoscale carbonaceous and silica slits of shale rocks. It is demonstrated that shale oil density does not remain the same throughout the pore and its oscillation attenuates from the slit surface to the central plane. In this paper, the effects of oil composition and temperature on the densities of the adsorption layers and adsorption character have been extensively examined. We find that (a) there are four adsorption layers of oil mixture on silica and graphite surface, (b) the adsorption character of single component in oil mixture depends largely on its property: the adsorption mass of high carbon number alkane increases with the numbers of adsorption layers, of which trend is contrary to that of light carbon numbers alkane; aromatic hydrocarbon has mainly one adsorption layer; the adsorption character of polar compounds depends on their electric charge, (c) silica surface is more likely to adsorb the light carbon number alkane than graphite because of its rough surface; and compounds with negative charge trend to be adsorption more on the silica surface than graphite due to the hydroxyls of silica. Graphite adsorbs more C10H8 than silica, because graphite and C10H8 have the same conjugated pi bond and the shape of C10H8 is not suitable to rough surface of silica, (d) the density of adsorption layers decreases with the increase of temperature, and the effect of temperature on the adsorption of macromolecular compounds is greater. On the basis of our molecular simulation, we show the adsorption rate of shale oil on the surfaces of mineral/organic matter and the potential to assess the moveable capacity of shale oil.