This work examines the influences of fault movement, induced fluid flow, and thermal mudstone evolution on the secondary porosity generation and diagenesis in Eocene–Miocene sandstones from the Western Bozhong depression, offshore Bohai Bay Basin, using quantitative petrographic analyses, stable isotopes, quantitative fluorescence, and quantitative evaluations of fault movement, seal, and fluid flow. Mudstones at shallow, moderate, and deep depths have different capacities in providing organic acids/CO2 for mineral dissolution and ions for the precipitation of carbonate cements in adjacent sandstones. Moderate and deep mudstones are mature and able to provide organic acids/CO2 and other ions to adjacent sandstones. However, shallow mudstones are not mature and have limited mass supply capacity. Subsequent fault movement activates fluid migration, resulting in the redistribution of organic acids/CO2 (including naphthenic acid/CO2 from hydrocarbon biodegradation), the acceleration of secondary porosity generation, and the export of byproducts. Under the joint influences of thermal mudstone maturity and fault movement-induced fluid flow, organic acids/CO2 could have been sourced from adjacent mudstone (internal source, deep model, >2500 m), transported from deep formations through faults (external source, shallow model, <2000 m), or both (mixed source, transition model, 2000–2500 m). As a result, deep, moderate, and shallow sandstones exhibit distinctive diagenetic models. This work presents a complete profile of diagenetic models from shallow to deep depths and may serve as a reference for the analysis of secondary porosity and sandstone diagenesis in analogous geological backgrounds.

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