Organic Pore Development Under the Influence of Mineral–Organic Interaction: Insights From ReaxFF Molecular Dynamics Simulations

Organic matter pores serve as the primary storage space for shale oil and gas, and their development degree is controlled by the hydrocarbon generation capacity of organic matter. However, the influence of mineral matrix on hydrocarbon generation capacity has not been fully investigated. In this study, the Permian Gufeng Formation shale (high carbonate mineral content) and the Silurian Longmaxi Formation shale (high clay mineral content) from the Sichuan Basin were selected. By integrating FE‐SEM, x‐ray photoelectron spectroscopy (XPS), 13 C nuclear magnetic resonance ( 13 C NMR), Fourier transform infrared spectroscopy (FT‐IR), elemental analysis, kerogen molecular modeling, and ReaxFF MD simulations, we systematically revealed how the mineral matrix influences the pyrolysis pathway of organic matter and the development of organic pores. SEM observations show that organic matter in contact with calcite appears dense and nonporous, whereas the development degree of organic pores significantly increases with higher clay mineral content or when organic matter is in contact with clay minerals. We constructed molecular models based on experimental data of the Gufeng Formation kerogen and performed ReaxFF MD simulations of kerogen pyrolysis from 300 to 3000 K in three environments: pure, montmorillonite interlayer, and calcite. The simulation results show that in the calcite environment, the Lewis acidity of Ca 2+ accelerates bridging bond cleavage in the early stage of pyrolysis; however, in the middle‐late stage, Ca 2+ forms stable complexes with oxygen‐containing functional groups and abstracts organic hydrogen to form H 2 O, leading to a deficiency of free hydrogen species in the system. This inhibits the generation of gaseous hydrocarbons (C 1 –C 4 ) and hinders pore development. In the montmorillonite environment, the synergistic catalysis of Brønsted and Lewis acid sites promotes C–C/C–H bond breaking, ring‐opening reactions, and decarboxylation/hydrocracking. This increases the yields of gaseous hydrocarbons (C 1 –C 4 ), light oil (C 5 –C 13 ), and heavy oil (C 14 –C 40 ), thereby providing a sufficient gas source for organic pore development. This study elucidates the intrinsic mechanism by which mineral matrix influences organic pore development through controlling hydrocarbon generation pathways and provides a micro‐scale theoretical basis for the evaluation of carbonate‐rich shale reservoirs.