摘要
全球范围下寒武统发育的黑色泥岩是一套重要的优质烃源岩。该套烃源岩分布广,但在不同地区厚度和质量差异大,重建其沉积与发育模式对预测优质烃源岩的分布具有重要意义,并可为页岩气勘探提供指导。通过对鄂西地区天柱山剖面下寒武统烃源岩样品开展有机碳、主量元素、微量元素等地球化学分析测试,探讨古气候、古生产力和古海洋环境等对优质烃源岩形成的控制作用,分析下寒武统优质烃源岩的沉积模式、发育机制以及生物活动和海洋环境变化与优质烃源岩形成的耦合关系,结果表明,天柱山剖面下寒武统优质烃源岩段具有高TOC含量(2.63%~8.76%)、高化学蚀变指数(68~76)和高生物来源Ba(平均含量为1392×10^-6)的特点,且高度富集氧化-还原敏感元素(Mo、U和V)。V/Cr比值、U/Th比值和V/Sc比值指示天柱山剖面下寒武统的水体经历了从硫化缺氧环境到次氧化环境再到氧化环境的变化,与Mo、U富集因子之比指示的氧化-还原环境变化特征相一致。TOC含量与Al、Si、生物来源Ba含量的相关性表明陆源输入对烃源岩有贡献。δ13 C的变化反映了海平面升降对生物生存环境有影响。研究认为,鄂西地区早寒武世海水的硫化缺氧和表层海洋生产力高是导致有机质大量埋藏、形成优质烃源岩的关键。
Black mudstones developed worldwide in Lower Cambrian strata are an important set of high-quality source rocks.Although this set of source rocks is widely distributed,its thickness and quality vary largely in different regions.Reconstruction of the sedimentary and developmental model for black mudstones is of great significance for predicting the distribution of high-quality source rocks and can provide guidance for shale gas exploration.The geochemical analyses of organic carbon,major elements,and trace elements were performed on source rock samples from Lower Cambrian strata in the Tianzhushan profile of western Hubei,aiming to explore the control effect of paleoclimate,paleoproductivity and paleo-marine environment on the formation of high-quality source rocks,to analyze the sedimentary model and development mechanism of Lower Cambrian high-quality source rocks and the coupling relationship between the changes of biological activities and marine environment and the formation of high-quality source rocks.The results show that the high-quality Cambrian source rock section of the Tianzhushan profile is characterized by high TOC content(2.63%-8.76%),high chemical index of alteration(68-76),high biogenic Ba content(average of 1392×10^-6)and high enrichment of redox sensitive elements(Mo,U and V).The V/Cr,U/Th and V/Sc ratios indicate that Lower Cambrian water in the Tianzhushan profile underwent changes from sulfurized anoxic environments to sub-oxidized environments and then to oxidized environments.This is consistent with the change characteristics of redox environment indicated by the ratio of Mo and U enrichment factors.The correlation between TOC and Al,Si,biogenic Ba contents indicates that terrestrial input made a contribution to source rocks.The change ofδ13 C reflects the influence of sea level eustacy on living environment.The study demonstrates that the sulfidation and anoxia of seawater and high marine productivity in Early Cambrian are key factors controlling the large-scale burial of organic matter
作者
赵坤
李婷婷
朱光有
张志遥
李婧菲
王鹏举
闫慧慧
陈永进
Zhao Kun;Li Tingting;Zhu Guangyou;Zhang Zhiyao;Li Jingfei;Wang Pengju;Yan Huihui;Chen Yongjin(School of Energy Resources,China University of Geosciences,Beijing 100083,China;Key Laboratory of Strategy Evaluation for Shale Gas,Ministry of Natural Resources,Beijing 100083,China;PetroChina Research Institute of Petroleum Exploration and Development,Beijing 100083,China)
出处
《石油学报》
EI
CAS
CSCD
北大核心
2020年第1期13-26,共14页
Acta Petrolei Sinica
基金
国家科技重大专项“塔里木盆地奥陶系—前寒武系碳酸盐岩油气资源潜力及目标优选”（2016ZX05004-004）
中国石油天然气股份有限公司科学研究与技术开发项目“古老碳酸盐岩油气成藏分布规模与关键技术”（2019B-04）和“深层烃源岩形成与分布”（2018A-0102）资助
关键词
优质烃源岩
下寒武统
古生产力
古海洋环境
发育模式
鄂西地区
high-quality source rocks
Lower Cambrian
paleoproductivity
paleo-marine environment
development model
western Hubei
