摘要
探讨陆相淡水湖盆页岩层段的有机质富集机理及主控因素,对于指导陆相页岩油气的勘探开发具有重要意义。四川盆地侏罗系自流井组的东岳庙段和大安寨段发育陆相页岩,油气勘探潜力巨大,其有机质富集机理有待探索。以自流井组页岩为研究对象,开展了岩心描述、薄片观察、扫描电镜、有机碳含量、干酪根镜检分析以及主微量元素测试,对沉积古环境进行恢复并明确了有机质富集主控因素。结果表明:自流井组页岩的有机碳含量为0.29%~3.43%,平均值为1.32%。干酪根类型指数主要分布在24~52之间,平均值37,表明有机质类型为Ⅱ1型和Ⅱ2型,有机质主要来源于藻类等水生生物与陆源高等植物的混合。古气候指标C值、Sr/Cu值、古风化指标CIA值以及古盐度指标Sr/Ba值表明,自流井组沉积时期四川盆地为一个潮湿气候条件下的淡水湖盆。湖盆水体的中等生产力为有机质的富集提供了较为充足的物质基础,富氧的底水环境导致有机质被氧化消耗不利于有机质的富集。TOC与多个古环境指标交汇图分析表明,自流井组页岩的有机质富集主要受到古生产力、古气候、沉积速率的控制。只有在相对潮湿的气候条件、相对较高的古生产力和适当的沉积速率背景下,有机质才会富集。氧化还原条件和盐度不是陆相淡水湖盆页岩有机质富集的主控因素,这与海相页岩和陆相咸水湖盆页岩存在较大差异。
It is of great significance to study the enrichment mechanism of organic matters and the associate main controlling factors of shale strata in continental freshwater lacustrine,which can guide the exploration and development of continental shale oil and gas.Lacustrine shales are developed in Dongyuemiao member and Da'anzhai member of Jurassic Ziliujing Formation in Sichuan Basin,which has great potential for oil and gas exploration.Its organic matter enrichment mechanism needs to be explored.Taking those shales in Ziliujing Formation as the research object,core description,thin section observation,electron microscopy scanning,measuring organic carbon content,kerogen microscopic analysis,and main and trace elements test were carried out to restore the sedimentary palaeoenvironment and then examine the main controlling factors of organic matter enrichment.The results show that the organic carbon content of Ziliujing Formation shale ranges from 0.29%to 3.43%,with an average value of 1.32%.Kerogen type index was mainly distributed in the range of 24-52,with an average of 37,indicating that organic matter was typeⅡ1 and typeⅡ2.Organic matter mainly came from the mixture of aquatic organisms,and terrestrial higher plants.The values of C,Sr/Cu,CIA,and Sr/Ba,and palaeo-salinity,proxies of palaeoclimates,indicate that the Sichuan Basin was a freshwater lacustrine in humid climate during the deposition of Ziliujing Formation.The medium productivity of lacustrine water provides sufficient material basis for the enrichment of organic matter.The oxygen-rich bottom water leads to the oxidation of organic matter,which is not favorable for the enrichment of organic matters.The analysis of cross plot of TOC and several palaeoenvironmental proxies show that organic matter enrichment in Ziliujing shales is mainly controlled by the palaeo-productivity,palaeo-climate,and deposition rate.Organic matter can be enriched only under the background of relatively humid climatic conditions,relatively high productivity,and appropriate dep
作者
张美洲
朱筱敏
姜振学
朱德宇
叶蕾
谌志远
ZHANG Meizhou;ZHU Xiaomin;JIANG Zhenxue;ZHU Deyu;YE Lei;CHEN Zhiyuan(State Key Laboratory of Petroleum Resources and Prospecting,China University of Petroleum(Beijing),Beijing 102249,China;College of Geosciences,China University of Petroleum(Beijing),Beijing 102249,China;Unconventional Oil and Gas Science and Technology Research Institute,China University of Petroleum(Beijing),Beijing 102249,China;Exploration and Development Research Institute,PetroChina Southwest Oil and Gas Field Company,Chengdu 610095,China)
出处
《古地理学报》
CAS
CSCD
北大核心
2023年第4期806-822,共17页
Journal of Palaeogeography：Chinese Edition
基金
中国石油天然气集团有限公司—中国石油大学(北京)战略合作科技专项(编号:ZLZX2020-02)资助。
关键词
四川盆地
侏罗系
自流井组
页岩
微量元素
有机质
主控因素
Sichuan Basin
Jurassic
Ziliujing Formation
shale
trace elements
organic matter
main controlling factor
