Surface chemistry and atomic-scale reconstruction of kerogen-silica composites

Interest in gas shale, a novel source rock of natural gas, has increased tremendously in recent years. Better understanding of the kerogen-rock interaction is of crucial importance for efficient gas extraction and, hence, asset management. In this study, we explore the possible chemical bonds between kerogen and silica, one of the most predominant mineral constituents of gas shale, by means of quantum chemistry. Energetically favorable bond formation reactions are found between alcoholic hydroxyl, carboxylate, and aldehyde groups, as well as aliphatic double bonds of kerogen and the silica surface. The performance of a reactive force field was also assessed in a representative set of chemical reactions and found to be satisfactory. The potential impact of bond formation reactions between the two phases on the actual kerogen-silica interface is discussed as a function of the kerogen type, maturity, and density. Finally, a methodology aiming to reconstruct realistic kerogen-silica interfaces is presented.