Abstract: Exploration practice indicates that the Jurassic Da’anzhai Member shale oil and gas in northeastern Sichuan show
broad exploration prospects, yet in-depth research on shale pore development and its controlling factors remains lacking. This study investigates the co-evolutionary process of hydrocarbon generation, diagenesis, and reservoir formation in the Da’anzhai shale through source-reservoir coupled pyrolysis experiments. The research demonstrates that: organic matter degradation and hydrocarbon generation, alkaline mineral dissolution, clay mineral transformation, and quartz mineral dissolution constitute the primary pore-enhancing factors during the evolution of the Da’anzhai shale, while alkaline mineral recrystallization, organic matter aromatization, and quartz secondary enlargement represent the main pore-reducing factors. Based on the organichydrocarbon generation evolution curve and mineral alteration characteristics during thermal evolution, a semi-quantitative analysis was conducted on the contributions of organic hydrocarbon generation and mineral transformation to shale pore development throughout the thermal evolution process. Furthermore, a co-evolution model for diagenesis-hydrocarbon generationreservoir formation of the Da’anzhai Member shale was established, dividing the pore evolution processes of the Da’anzhai shale into four stages: The Middle Diagenetic substages A1 (Ro=0.79%-1.09%), A2 (Ro=1.09%-1.28%), B1 (Ro=1.28%-1.47%), and B2 (Ro=1.47%-2.02%) exhibit distinct evolutionary characteristics. Significant shale porosity increment primarily occurs during the Middle Diagenetic Substage A2, which corresponds to the peak oil generation stage of organic matter. This demonstrates that hydrocarbon generation from organic matter substantially contributes to pore development in the Da’anzhai Member shale, providing critical insights into understanding the reservoir evolution patterns in northeastern Sichuan’s Da’anzhai Formation.

Key words: shale pore evolution, source-reservoir coupled evolution simulation experiment, diagenesis, hydrocarbon generation;
Da’anzhai Member, Northeastern Sichuan