中国陆相富有机质页岩沉积速率研究及其页岩油勘探意义

Investigation of deposition rate of terrestrial organic-rich shales in China and its implications for shale oil exploration

张瑞 金之钧 朱如凯 李明松 惠潇 魏韧 贺翔武 张谦

Rui ZHANG Zhijun JIN Rukai ZHU Mingsong LI Xiao HUI Ren WEI Xiangwu HE Qian ZHANG

页岩的有机质丰度和纹层类型是页岩油勘探研究的重点内容。中国陆相富有机质页岩层系的沉积相变复杂且非均质性强，沉积速率的准确判识面临许多挑战。中国典型陆相盆地富有机质页岩的沉积速率多在5 cm/kyr以上，咸化湖盆富有机质页岩层系沉积速率最高可达40 cm/kyr。高精度年代学框架结合旋回地层学统计调谐可以追踪沉积速率随地层深度的变化，而页岩的相对沉积速率可以通过稀土元素配分模式、晶体粒径分布理论和星际尘埃特征元素丰度等方法判识。不同类型或不同时代的地层序列沉积速率比较，需要考虑地层完整性和差异压实等干扰因素。沉积速率是页岩有机质富集的重要影响因素，其对有机质稀释的临界值通常低于5 cm/kyr。水动力条件和水体盐度影响碎屑颗粒的絮凝作用，不同类型细粒沉积物的沉积速率差异有利于纹层结构的形成。页岩沉积速率研究需要融合包括地质年代学、岩石学、旋回地层学、地球化学和沉积物理模拟在内的先进理论和方法，以深入了解页岩沉积演化机理。揭示陆相页岩沉积速率与页岩油富集之间的内在联系，对页岩油勘探具有一定的指导意义。

The abundance of organic matter and the types of shale laminae are the key in shale oil exploration. The sedimentary facies of terrestrial shales features complex variation and strong heterogeneity， making accurate identification of deposition rate facing more challenges. The deposition rates of organic-rich shales in typical terrestrial basins of China are mostly above 5 cm/kyr， and those of the organic-rich shales in saline lacustrine basins may reach up to 40 cm/kyr. The high-precision chronostratigraphic framework combined with the statistical tuning of cyclostratigraphy can trace the variation of deposition rate with burial depth. The relative deposition rate of shales can be determined by the rare earth element （REE） assemblage pattern， crystal size distribution， and the abundance of typical interstellar dust elements， etc. Comparison of deposition rates of different types or ages of stratigraphic sequences has to take perturbations such as stratigraphic integrity and differential compaction into consideration. Deposition rate is an important factor influencing the enrichment of organic matter in shale， and the critical threshold for organic matter dilution by deposition rate is usually less than 5 cm/kyr. The flocculation of sediment particles is usually under the effect of hydrodynamic conditions and water salinity， and the various deposition rates for different types of fine-grained sediment are conducive to the formation of shale laminae. The study of deposition rate requires an integration of advanced theories and methods， including geochronology， petrology， cyclostratigraphy， geochemistry， and physical simulation of sedimentation， to gain a deeper understanding of the mechanisms of shale deposition and evolution. Revealing the interrelationship between terrestrial shale deposition rate and shale oil accumulation is of certain guiding significance to shale oil exploration.

10.11743/ogg20230403