天文周期驱动下湖相细粒沉积岩有机质富集模式——以东营凹陷LY1井沙三下—沙四上亚段为例  

Organic Matter Enrichment Model of Lacustrine Fine-grained Sedimentary Rocks Driven by Astronomical Cycles:A case study of the lower Es3 and upper Es4 sub-member in well LY1,Dongying Sag

作　　者：王浡 石巨业 朱如凯[2,3] 梁新平 WANG Bo;SHI JuYe;ZHU RuKai;LIANG XinPing(School of Energy Resources,China University of Geosciences(Beijing),Beijing 100083,China;Institute of Energy,Peking University,Beijing 100871,China;Research Institute of Petroleum Exploration&Development,PetroChina,Beijing 100083,China)

机构地区：[1]中国地质大学(北京)能源学院,北京100083 [2]北京大学能源研究院,北京100871 [3]中国石油勘探开发研究院,北京100083

出　　处：《沉积学报》2025年第2期750-768,共19页Acta Sedimentologica Sinica

基　　金：国家自然科学基金项目(42102150)。

摘　　要：【目的】东营凹陷湖相细粒沉积岩具有巨大的非常规油气资源前景,然而由于其粒度小、相变快、层序界面不易识别等难点,传统层序地层学无法准确进行地层划分与对比,使得其有机质富集模式认识不清,制约了非常规油气勘探推进。旋回地层学可以进行高频层序的划分和地层的精细对比,还可以探究天文周期驱动细粒岩沉积的过程,是建立有机质富集模式进而预测页岩油甜点层段重要手段。【方法】以渤海湾盆地东营凹陷LY1井为例,基于岩心、地球化学和自然伽马测井数据对沙三下—沙四上亚段湖相细粒沉积岩进行旋回地层学分析。【结果】(1)该套地层记录了良好的天文周期信号,沙三下亚段主要受控于偏心率和岁差周期,沙四上亚段主要受控于偏心率和斜率周期;(2)利用稳定的405 kyr长偏心率天文调谐,以沙三下亚段顶部年龄39.40 Ma为锚点,建立起绝对天文年代标尺;(3)将长偏心率、短偏心率、斜率的滤波曲线分别作为四、五、六级层序划分的参考曲线,划分出10个四级层序、40个五级层序,进一步以区域对比特征显著的长偏心率为标尺进行连井对比,建立全区高精度等时地层格架。【结论】通过探讨细粒沉积岩对偏心率、岁差周期响应,提出暖湿、干冷两种气候条件下有机质富集模式,认为在偏心率极大值附近有利于有机质富集。[Objective]The lacustrine fine-grained sedimentary rocks in Dongying Sag have great prospects for unconventional oil and gas resources.However,owing to the small grain size,rapid phase transition,and difficult identification of sequence interface,the traditional sequence stratigraphy cannot accurately divide and contrast the strata.At present,the understanding of the organic matter enrichment model is unclear,limiting the progress of unconventional oil and gas exploration.Cyclostratigraphy can divide high-frequency sequences and conduct a fine stratigraphic correlation,and can also explore the process of fine-grained rock deposition driven by astronomical cycles,which is an important means to establish the organic matter enrichment model and predict the sweet spot of shale oil.[Methods]Taking well LY1 in Dongying Sag,Bohai Bay Basin,as an example,the cyclostratigraphy of lacustrine fine-grained sedimentary rocks in the lower Es_(3)(Es_(3)^(l))and upper Es_(4)(Es_(4)^(u))sub-member were analyzed based on core,geochemical analysis,and natural gamma logging data.[Results](1)The results show that this set of strata records good astronomical period signals,Es_(3)^(l) is mainly controlled by eccentricity and precession period,and Es_(4)^(u) is mainly controlled by eccentricity and obliquity period.During the deposition of Es_(3)^(l),the thickness of sedimentary cycles controlled by 405 kyr long eccentricity,100 kyr short eccentricity,and 20 kyr precession were 46.34 m,14.2012.23 m,and 2.64-2.09 m,respectively;while during that of Es_(4)^(u),the thickness of sedimentary cycles controlled by 405 kyr eccentricity,40 kyr obliquity,and 20 kyr precession were 30.54 m,4.00-3.01 m,and 1.83-1.23 m,respectively.From Es_(4)^(u) to Es_(3)^(l),the driving and controlling factors of sedimentary cycle gradually changed from the obliquity to precession cycle.(2)A 39.40-43.47 Ma absolute astronomical time scale was established using stable 405 kyr eccentricity astronomical tuning,with the top age of Es_(3)^(l) at 39.40 Ma as the anchor

关 键 词：东营凹陷 旋回地层学 细粒沉积岩 天文年代标尺 高频层序 有机质富集 

分 类 号：P618.13[天文地球—矿床学]