Lacustrine Shale Pore Structure Influenced by Diabase Intrusions in the Cretaceous Taizhou Formation, Subei Basin,...

The influence of diabase intrusion on the pore structure is crucial when attempting to understand petroleum accumulation for unconventional reservoirs. This study aims to characterize the pore structure of shale affected by diabase intrusion. A total of 15 core samples were employed to analyze the pore structure characteristics through X-ray diffraction, thin section analysis, scanning electron microscopy, total organic carbon content, nitrogen adsorption, and high-pressure mercury intrusion experiments. The contact metamorphic zone is divided into high-grade metamorphic, low-grade metamorphic, and normal shale zones according to lithology differences. The porosity and permeability of the low-grade metamorphic zone are much better than the other two zones. In addition, the mesopores and macropores in the low-grade metamorphic zone have a more specific surface area, total pore volume, and a lower pore radius than the others. The diabase intrusion increases the mesoporous structure's complexity but reduces the macropores' pore structure heterogeneity. Overall, the diabase intrusion improves the low-grade metamorphic zone and has a negative impact on the high-grade metamorphic zone. Diabase intrusion impacts the pore structure by interacting with fluids, pressure, temperature, and mechanical-thermal-chemical processes. This study provides a quantitative foundation for assessing and predicting shale oil resources in diabase intrusion areas within terrestrial basins.