川东北地区油气形成过程中稀土元素地球化学特征  

REE geochemical characteristics petroleum and gas formation northeastern Sichuan basin

作　　者：李靖[1,2] 周世新[1] 郑朝阳[1] 王保忠[1,2] 柳少鹏[1,2] 张海坤[1,2] 巩书华[1,2] 

机构地区：[1]中国科学院地质与地球物理研究所油气资源研究重点实验室,甘肃兰州730000 [2]中国科学院大学,北京100049

出　　处：《中国矿业大学学报》2013年第4期606-615,645,共11页Journal of China University of Mining & Technology

基　　金：中国科学院知识创新工程重要方向项目(KZCX2-YW-Q05-03);国家重点基础研究发展规划(973)项目(2011CB201102)

摘　　要：针对我国海相烃源岩成熟度高、油气源对比困难的特殊性,以川东北地区古生界—中生界为研究对象,对有机质(烃源岩干酪根、沥青)的稀土元素特征进行分析,并对有机质中稀土元素的来源进行了探讨,通过稀土元素与有机碳同位素数理统计分析,对古油藏油源进行辨别,为高过成熟度地区油源对比提供了一种新的方法.研究结果表明:研究区有机质的稀土元素总量变化范围为0.23～603.39μg/g,比赋存环境大;干酪根δEu变化范围为0.71～1.06,比全岩低,主要反映有机质沉积时的还原环境;干酪根的轻、重稀土元素比为1.01～16.73,相比其全岩呈重稀土元素富集,富集程度由老地层向新地层逐渐增强,其变化趋势与有机质碳同位素呈较明显的负相关,表明有机质中稀土元素主要继承自原始有机物质,可作为有机物源研究的指示剂.数理分析综合对比表明,该区上震旦系古油藏的主要烃源岩层为下寒武统,上二叠统—下三叠统古油藏的主要烃源岩层为上二叠统和上奥陶统.Because marine source rock has high maturity in China and the difficulty exists in gas-oil source correlation,this paper took Palaeozoic erathem and Mesozoic erathem of northeastern Sichuan basin as a case in point,and studied the characteristics of REE of organic matter（such as source rock kerogen and pitch）,then explored the origin of REE in organic matter.Mathematical statistic analysis of REE and organic carbon isotope as well as distinguishing the paleo-oil reservoir provides a new method of oil-source correlation in high maturity region.The results show that： variation of REE in organic matter ranges from 0.23 to 603.39 μg/g,greater than occurrence environment;variation range of kerogen δEu is from 0.71 to 1.06,lower than whole rock,indicating a reducing environment of organic matter deposit.The ratio of ∑LREE/∑HREE of kerogen ranges from 1.01 to 16.73,showing the abundance of heavy REE compared with total rock and gradually increasing from old strata to new strata,with a negative correlation with δ13 Corg.It indicates that REE in organic matter is mainly from the original organic matter,and could be a good indicator in analysis of organic matter.By comprehensive analysis of REE and organic data of organic matter from Palaeozoic and Mesozoic of northeastern Sichuan basin,it concludes that that the main provenance layer of paleo-oil reservoir in Upper Sinian is Lower Cambrian,and the main provenance layer of paleo-oil reservoir in Upper Permian-Lower Triassic is Upper Permian and Upper Ordovician strata.

关 键 词：有机质 稀土元素(REE) 油源对比 川东北地区 

分 类 号：TE122[石油与天然气工程—油气勘探]