Progress in the study of kinetic mechanism of kerogen maturity evolution

[ Instrument R&D of Instrument Network ] Kerogen, as the main parent material for shale oil and gas generation, is the most important form of organic carbon on earth. The kerogen maturity reflects the geological stage of organic matter, and its evolution process is accompanied by oil and gas generation, adsorption, accumulation and migration, which is an important indicator for evaluating source rocks. Therefore, studying the evolution law of kerogen maturity and exploring its time-temperature-maturity relationship has always been the key research direction of shale oil and gas exploration and development.

Recently, the team of Zhao Yapu, a researcher from the State Key Laboratory of Nonlinear Mechanics, Institute of Mechanics, Chinese Academy of Sciences, constructed a three-dimensional kerogen macromolecular model of China’s deep shale, and studied the chemical-mechanical coupling effect during its thermal evolution. A new kerogen maturity evaluation index (Molecular Maturity Index, MMI). Pyrolysis experiments and molecular dynamics simulation results show that the weight loss rate of kerogen has a positive linear correlation with MMI, proving that the index can reflect the hydrocarbon generation capacity of kerogen. They also introduced a new kinetic conversion rate based on MMI and established a continuous equation of activation energy related to maturity. Based on the conversion rate, a new chemical kinetic model of kerogen maturity evolution (MEKM) is further obtained, and the time-temperature-maturity relationship of kerogen is established. Its form is simple and convenient for engineering. application. This work is helpful to understand the microscopic mechanism of kerogen cracking to generate oil and gas, provide guidance for the related technologies of artificial ripening kerogen, and promote the reduction of shale oil and gas development costs.

The related results were published in the international mainstream academic journal Fuel (Wang XH and Zhao YP*, Fuel. 2020, titled The time-temperature-maturity relationship: a chemical kinetic model of kerogen evolution based on a developed molecule-maturity index 278: 118264). The research was supported by the National Natural Science Foundation of China and the Chinese Academy of Sciences' cutting-edge key research projects.