典型蒸发岩与泥岩共生沉积体系中元素及烃类物质响应

——以东营凹陷沙四段为例

陈中红,等。地质学报，2009，83（3）：435-445

内容提要：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心，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40 mg/g和20 mg/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。

关键词：无机元素；碳同位素；生、排烃潜力；蒸发岩；东营凹陷

Response of Mineral Elements, Carbon Isotope and Hydrocarbon in Typical Co-Sedimentary System of Evaporates and Mud in Lacustrine Basin:A Case Study from the Dongying Sag, Bohai Bay Basin

CHEN Zhonghong, et al. ACTA GEOLOGICA SINICA, 2009，83（3）：435-445

China University of Petroleum, Dongying, Shandong, 257061

The middle and lower parts of 4^th Member of Shahejie Formation in Dongying sag were the representative co-sedimentary system of evaporates and mud rocks in the Eastern of China. To investigate the response of mineral elements, carbon isotope and hydrocarbon generation of co-sedimentary system of evaporates and mud rocks the saline formation of two deep wells (Haoke-1 well and Fengshen-2 well) in the sag were intensively cored, tested and dissected.

The results demonstrate that: there were remarkable response of formation water field and the content of total salinity and chloride ion was very high, and the type water of CaCl₂ was dominated, which displayed the favorable conditions of sealing and conservation; different minerals have various response, the content of Al, Mn, Ba and the parameter of V/Ni, (Fe+Al)/(Ca+Mg) have low value responses, and the content of Na, Ca, Mg and the parameter of Sr/Ba, Fe/Mn, Sr/Ca were highly responded, especially the content of Sr displayed remarkable high value. The distribution of mineral elements had obvious characteristics of discretion and fluctuation, and the mineral elements are discrepancy in the saline deposits and enriched in the adjacent mud (except for Na, and Na enriched in the saline deposits); the value δ¹³C of different group compositions and composition of n-alkane was respectively ranged from -28‰~-21‰ and -18‰~-32‰, the fractionation of δ¹³C between group compositions was no more than -2‰,and  there was marked fluctuation in C₁₇、C₁₈. The value of δ¹³C of carbon isotope of residual hydrocarbon from source rocks was increased by thermal evolution and TSR reaction. The co-sedimentary system of evaporates and mud had potential capacity of hydrocarbon generation and expulsion. The tested samples were typeⅠand typeⅡ₁ of organic matter, and their original potential capacity of hydrocarbon generation and expulsion can reached 40 mg/g and 20 mg/g, and the efficiency of hydrocarbon expulsion attained 60%, but the distribution of organic matter and its potency of hydrocarbon generation and expulsion had stronger heterogeneity. The content and maturity of organic matter and its potency of hydrocarbon generation and expulsion from the mud were higher than the evaporates’s in the co-sedimentary systems.

Key words: mineral element; carbon isotope; evaporates; potency of hydrocarbon generation and expulsion; Dongying sag

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