湘西碳沥青若干微量元素地球化学特征

Geochemistry of trace elements in the anthraxolite from Xiangxi

为分析碳沥青的微量元素地球化学特征,采用Element XR等离子体质谱分析仪及对选取的碳沥青样品进行测试。结果显示,碳沥青的微量元素丰度与页岩、围岩差异明显,其中V(1039.40μg/g)、Ni(345.90μg/g)、Sr(227.67μg/g)和Mo(64.70μg/g)显著富集。对以上4种元素的赋存和富集模式进行分析,结果表明:元素V和Ni在碳沥青中富集的主要原因包括,继承了原油微量元素特征、较强的螯合作用和油气演化3个方面,在本身绝对含量不减或微增的情况下,其他元素和有机质总量的亏损在一定程度上突出了V和Ni的相对富集;Mo与V、Ni具有相似的赋存和富集机理,Sr的富集可能与油气运移过程中对地层中Sr的溶解和储层热演化过程中的有机质络合作用有关,但是也可能与Sr尚不明确的地球化学行为有关。

The Element XR was used to analyze the geochemical characteristics of elements in the anthraxolite. The results show that the element abundance of anthraxolite is apparently different from that in shale and surrounding rock. Furthermore, V（1039.40 μg/g）, Ni（345.90 μg/g）, Sr（227.67 μg/g） and Mo（64.70μg/g） have significant enrichment. Analysis of the occurrence and enrichment pattern of the four elements shows that the enrichment of V and Ni in anthraxolite is the comprehensive effect of three aspects, including the trace element characteristics in crude oil, strong chelation and evolution of crude oil. With the absolute content of the element not reduced or even incremental, the loss of other elements and organic matter extrudes the relative enrichment of V and Ni to some extent. Mo shares the similar occurrence and enrichment mechanisms with V and Ni. The concentration of Sr may be related to the dissolution of Sr in the stratum during the migration process of crude oil, and the organic complexation in the heat evolution process of oil in the reservoir, but it may also be related to the unclear geochemical behavior of the element Sr.