鄂尔多斯盆地长7_(3)亚段页岩有机质含量非均质性分布及成因  

Heterogeneous characteristics and genesis of shale in Chang 7_(3) sub member Ordos Basin

作　　者：刘伟[1] 刘江艳 李继宏[2,3] 董劲[1] 高阳 张岩[2,3] 刘婷婷[1] 柴世龙[1] Liu Wei;Liu Jiangyan;Li Jihong;Dong Jin;Gao Yang;Zhang Yan;Liu Tingting;Chai Shilong(Research Institute of Petroleum Exploration and Development,Beijing 100083;National Engineering Laboratory for Exploration and Development of Low Permeability Oil&Gas Fields,Xi'an 710018;Exploration and Development Research Institute of PetroChina Changqing Oilfield Company,Xi'an 710018)

机构地区：[1]中国石油勘探开发研究院,北京100083 [2]低渗透油气田勘探开发国家工程实验室,西安710018 [3]中国石油长庆油田分公司勘探开发研究院,西安710018

出　　处：《地质科学》2025年第2期484-496,共13页Chinese Journal of Geology(Scientia Geologica Sinica)

基　　金：国家自然科学基金项目“中低成熟度陆相页岩油资源形成与原位转化开采机理”(编号:U22B6004);中国石油勘探开发基金项目:研究院科学研究与技术开发项目“典型陆相中高熟页岩油富集特征与富集区评价”(编号:2022yjcq03)资助。

摘　　要：延长组长7_(3)亚段是鄂尔多斯盆地重要的烃源岩层系和页岩油勘探领域,研究其形成过程不仅有助于了解盆地演化,对页岩油精细勘探也有借鉴意义。前期重点关注了长7_(3)在延长组内的特殊性,但忽略了其自身的非均质性。本次研究选取深湖相区G135井为研究对象,基于岩石学、地球化学等分析,探讨了目的层段有机质含量非均质性特征及成因。研究表明,长7_(3)亚段可以分为3部分,中段有机质含量最高,下段次之,上段最低,古湖泊演化是导致有机质非均质分布的主要原因。长7_(3)亚段经历了早期快速湖侵、中期最大湖泛和晚期缓慢湖退的演化过程。在总体温暖湿润气候背景下,早-中期火山活动带来的营养物质导致生物勃发,同时硫酸根离子进入水体,加强了淡水湖盆的BSR反应,增强水体的还原性,引起有机质超量富集。(Fe+Mn)/Ti和碳酸盐矿物含量表明,中期发生的强烈热液活动加剧了这一过程,湖盆底部水体表现为强还原环境,更加有利于有机质保存。晚期随着火山和热液活动减弱,水体环境逐渐恢复正常,湖退背景下,泥岩比例增加,因此有机质含量总体偏低。Chang 7_(3) sub⁃member is the important hydrocarbon source rock and shale oil exploration domain in Ordos Basin.Study on formation process is not only helpful to understand evolution of the basin,but also of great significance for shale oil exploration.Previous studies focused on the particularity of Chang 7_(3) in Yanchang Formation,but ignored its own heterogeneity.In this work,G135 well is selected as the research object.Based on the analysis of petrology and geochemistry,the heterogeneity and genesis of the target interval are discussed.The research shows that according to the parameters such as mineral composition,organic matter content and logging curve characteristics,the Chang 7_(3) sub⁃member can be divided into three parts,with the highest TOC in the middle section,the second in the lowest section and the lower in the upper section.It experienced the evolution process of rapid lake transgression in early stage,maximum lake flooding in middle stage and slow lake regression in late stage.In warm and humid climate background,nutrients from volcanic activities in the early and middle stages led to the thriving of organism proliferation,which improved primary productivity and cause the excessive enrichment of organic matter.At the same time,sulfate ions from volcanic ash strengthened the BSR reaction in the freshwater basin and enhanced the reductivity of the water body.Contents of(Fe+Mn)/Ti and carbonate indicate that intense hydrothermal activity occurred in the middle stage which exacerbated this process.The water body at the bottom shows a strong reductive environment,which was more conducive to the preservation of organic matter.In the late stage,with the weakening of volcanic and hydrothermal activities,water environment gradually returned to normal,and proportion of mudstone increased under the background of lake retreat.

关 键 词：鄂尔多斯盆地 长7_(3)亚段 页岩 非均质性 沉积演化 

分 类 号：P618.13[天文地球—矿床学]