典型蒸发岩与泥岩共生沉积体系中元素及烃类物质响应——以东营凹陷沙河街组四段为例  

Response of Mineral Elements,Carbon Isotope and Hydrocarbon in Typical Synsedimentary System of Evaporate and Mudstone:A Case Study of the Dongying Sag,Bohai Bay Basin

作　　者：陈中红[1] 查明[1] 金强[1] 

机构地区：[1]中国石油大学(华东)地球资源与信息学院,山东东营257061

出　　处：《地质学报》2009年第3期435-444,共10页Acta Geologica Sinica

基　　金：国家自然科学基金(编号40272061);山东省自然科学基金(编号Q2007E04)资助成果

摘　　要：东营凹陷沙四段中、下亚段是中国东部典型的新生代第三系蒸发岩与烃源岩共生沉积体系。对其中两口深层井(郝科1井、丰深2井)沙四段含盐层段进行了较密集的取芯,对其中无机元素组成特征、碳同位素及有机质丰度、成熟度、生烃指标等进行了测试及分析,分析结果显示:不同元素响应差异明显,铝及锰、钡含量为低值响应,钠、钙、镁含量为高值响应,锶含量显示异常高值;特征元素比值分布上也有明显响应,V/Ni、(Fe+Al)/(Ca+Mg)出现低值响应,Sr/Ba、Fe/Mn、Sr/Ca均出现高值响应;元素分布离散性和波动性比较明显,无机元素在蒸发岩中亏损,而在相邻泥岩中相对富集(钠除外,钠在蒸发岩中富集);不同族组分和正构烷烃单体烃碳同位素值分别分布于-28‰～-21‰和-32‰～-18‰,有机质族组分间碳同位素分馏效应相对小(<-2‰),正构烷烃单体烃碳同位素曲线上,C17、C18的δ13C值相对较高而变化显著;热演化和TSR反应造成对烃源岩中残留烃类碳同位素δ13C值的增重作用;所检测含盐井段具有良好的生、排烃能力,有机质组分中腐泥组占绝对优势,有机质类型为Ⅰ型和Ⅱ1型,烃源岩原始生烃潜量及排烃量可分别达到40mg/g和20mg/g,排烃效率基本在60%以上,但它在平面上和剖面上均具有较强的非均质性。与蒸发岩共生的泥岩有机质丰度、成熟度及生、排烃各项指标要高于蒸发岩,高热演化可导致其残余生排烃能力下降。A typical Mesozoic（Tertiary） synsedimentary system of evaporate and mudrock occurs in the middle and lower parts of the 4th Member of Shahejie Formation in the Dongying sag,East China.To investigate mineral elements,carbon isotope,and hydrocarbon generation of synsedimentary evaporate and mudstone,an intense sampling for saline section was conducted in two deep wells（well Haoke-1 and well Fengshen-2） in the Dongying Sag.The results show remarkable response differences,characterized with low contents in Al,Mn and Ba,high in Na,Ca and Mg,and abnormally high in Sr and a distinct response of distribution of feature element ratios,low V/Ni,and（Fe＋Al）/（Ca＋Mg）,and high Sr/Ba,Fe/Mn and Sr/Ca.The distribution of mineral elements displays clear discretion and fluctuation inorganic elements is depleted in evaporate but enriched in neighboring mudstone（except sodium,which is also enriched evaporate）.δ13C values of different group compositions and n-alkane composition range from-28‰ to-21‰ and-18‰ to-32‰,respectively.δ13C factionation between compositions of organic group is relatively low（less than-2‰）,while n-alkane shows a distinct δ13C change in C17 and C18.The δ13C value of residual hydrocarbon from source rock was increased by thermal evolution and TSR reaction.The synsedimentary system of evaporates and mudstone has potential capacity of hydrocarbon generation and expulsion.The organic matter dominates decayed mud and can be divided into type Ⅰ and type Ⅱ1The original potential capacity of hydrocarbon generation and expulsion can reach 40 mg/g and 20 mg/g,and the efficiency of hydrocarbon expulsion attained 60%.But they both show intense heterogeneity in both plane and cross section.The content and maturity of the mudstone and generation and expulsion of hydrocarbon are higher than those of evaporate.In addition,high thermal evolution is likely to result in decreasing of generation and expulsion of residue hydrocarbon.

关 键 词：无机元素 碳同位素 生、排烃潜力 蒸发岩 东营凹陷 

分 类 号：P618.13[天文地球—矿床学]