Shale oil occurrence and mobility mechanisms in brittle mineral-enriched reservoirs: Insights from the Paleogene Kongdian Formation, Bohai Bay Basin

作者：Bixiao Xin, Fang Hao, Jinqiang Tian, Pengfei Guo, Qilu Xu, Wenzhong Han · 发表于：Geoscience Frontiers · 年份：2025 · DOI：10.1016/j.gsf.2025.102149 · 被引用次数：7 · 研究领域：Hydrocarbon exploration and reservoir analysis、Geological Studies and Exploration、Geological and Geophysical Studies

Understanding shale oil occurrence and mobility is essential for evaluating resource potential and optimizing exploration in lacustrine shale systems. This study investigates the Paleogene Kongdian Formation in the Bohai Bay Basin, integrating organic geochemistry, mineralogical analysis, scanning electron microscopy, solvent extraction, multi-step Rock-Eval pyrolysis, and 2-D NMR to characterize shale oil occurrence states and mobility mechanisms in brittle mineral-enriched reservoirs. Results indicate that shale oil mainly occurs in free and adsorbed states within interparticle pores, dissolution pores, microfractures, and organic pores, with most retained oil hosted in nanopores smaller than 200 nm. Quantitative analyses show that siliceous and calcareous shales possess higher movable oil ratios than clay-rich counterparts, primarily due to their rigid mineral frameworks that resist compaction and preserve interparticle and intragranular pores. These brittle-rich lithofacies exhibit broader pore size distributions, enhanced connectivity, and reduced adsorption affinity, facilitating more efficient oil accumulation and displacement. In contrast, micropore-dominated, clay-rich shales exhibit strong adsorption and limited pore continuity, which hinder hydrocarbon mobility. Appropriate TOC levels (2.0–4.5 wt%) favor shale oil mobility, while excessive organic content increases adsorption, reducing the proportion of free oil. Among various geological factors, brittle mineral co...