Reaction Kinetics Study on Hydrocarbon Generation of Medium- and Low-Maturity Organic-Rich Shale in Supercritical Water

In this study, the dominant path of hydrocarbon generation in supercritical water of granular medium- and low-maturity organic-rich shale is determined as well as the mechanism of supercritical water in the process of hydrocarbon generation of granular medium- and low-maturity organic-rich shale. The kinetics of hydrocarbon generation in supercritical water from granular medium- and low-maturity organic-rich shale was studied. A dynamic model of the hydrocarbon generation reaction of granular medium- to low-maturity organic-rich shale in supercritical water was constructed. The Runge–Kutta fourth-order algorithm and basin hopping algorithm were used to solve the fitting parameters. The model consisted of 11 parallel first-order reactions, which could accurately predict the mass fraction of the hydrocarbon generation products of granular medium- and low-maturity organic-rich shale in supercritical water and reveal the mechanism of the hydrocarbon generation reaction of medium- and low-maturity organic-rich shale in supercritical water. It was found that the hydrocarbon generation pathways of granular medium- and low-maturity organic-rich shale in supercritical water mainly consisted of direct generation of asphaltenes and saturated hydrocarbons from kerogen, pyrolysis of asphaltenes to saturated hydrocarbons, aromatic hydrocarbons, and resins, polymerization of resins to asphaltenes, and gas generation from saturated hydrocarbons, resins, and asphaltenes. The role of supercritical water facilitated the direct generation of saturated hydrocarbons from kerogen.