湖相细粒沉积岩有机质富集机理研究进展及其对页岩油勘探的启示

Research Progress on Organic Matter Enrichment Mechanisms in Lacustrine Fine-Grained Sedimentary Rocks and Its Implications for Shale Oil Exploration

摘要: 湖相烃源岩是中国陆相含油气盆地非常重要的油气母岩，有机质富集机理是油气有机地球化学与细粒沉积学交叉领域的前沿命题。本文基于近半个世纪以来国内外研究，系统梳理了湖相细粒沉积岩有机质富集的研究进展：湖泊类型与湖盆充填方式通过控制可容纳空间与沉积物供给，决定烃源岩发育的宏观格架；有机质富集受古生产力、氧化还原保存条件、沉积速率与稀释效应等主控因素的联合制约，并受古气候、天文轨道旋回以及构造–火山–热液事件的显著调制。元素地球化学、生物标志化合物与稳定同位素指标体系为恢复古环境、判识有机质来源与富集机制提供了有效手段。围绕“生产力论”与“保存论”的经典之争，越来越多的研究强调二者在不同湖盆、不同层段中的相对贡献差异，并逐步走向“生产力–保存–稀释”多元耦合的定量评价框架。本文以鄂尔多斯、松辽、渤海湾、准噶尔等盆地典型湖相层系为例进行对比，进而讨论了有机质富集研究对陆相页岩油“甜点”评价的启示，并展望了多指标解耦、深时天文驱动与数据驱动评价等未来方向。

Abstract: Lacustrine source rocks constitute the very important hydrocarbon mother rocks in non-marine petroliferous basins of China, and the mechanism of organic matter (OM) enrichment is a frontier topic at the interface of petroleum organic geochemistry and fine-grained sedimentology. Based on domestic and international studies over the past half century, this review systematically summarizes the progress on OM enrichment in lacustrine fine-grained sedimentary rocks. Lake type and basin-fill style control the macroscopic framework of source rock development through accommodation and sediment supply. OM enrichment is jointly governed by paleoproductivity, redox preservation conditions, sedimentation rate and dilution effects, and is significantly modulated by paleoclimate, astronomical orbital cycles, and tectonic-volcanic-hydrothermal events. Elemental geochemical, biomarker compound and stable isotope indicator systems provide effective tools for reconstructing paleoenvironments and identifying OM sources and enrichment mechanisms. With respect to the classical controversy between the “productivity model” and the “preservation model”, increasing evidence emphasizes the variable relative contributions of the two factors in different lake basins and intervals, and the framework of “productivity-preservation-dilution” coupling is being established. Typical lacustrine successions in the Ordos, Songliao, Bohai Bay and Junggar basins are compared, and the implications of OM enrichment studies for shale oil “sweet spot” evaluation are discussed. Future directions including multi-proxy decoupling, deep-time astronomical forcing and data-driven evaluation are proposed.