Abstract

A new oil show, Zelenseep, was discovered on the eastern shore of Middle Baikal. It is characterized by natural gas discharge (seep) from the lake floor and by accumulation of oil (high- molecular-weight bitumen fraction) and gas hydrates in the top layer of the sediments. The gas in the sediments and gas hydrates is composed of 99% thermogenic methane. The carbon isotope composition (δ¹³(С–С₁)) ranges from –48.1 to –48.8‰ for methane in the sediment and from –49.4 to –50.2‰ for that in the hydrates. Oil is not discharged into the water column. N-alkanes and isoprenoids are not found in the oil; polycyclic aromatic hydrocarbons are detected at the 1800– 2200 ppm level, including 50–90 ppm of rethene and 120–140 ppm of perylene. The perylene concentration evidences major transformation undergone by the oil on its migration path from the source. The presence of rethene in the oil is indicative of its continental origin, and that of biomarkers, hopanes, of its identity with the Baikal naphthenic-aromatic oils. The sediments of earlier Cenozoic age in Baikal Basin, occurring in its central deep-water part, were assigned to organic matter source.

中文翻译：

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贝加尔湖的新石油和天然气渗漏

摘要

在中贝加尔湖东岸发现了一个新的石油展，Zelenseep。其特点是天然气从湖底排出（渗出），石油（高分子量沥青馏分）和天然气水合物在沉积物的顶层聚集。沉积物和天然气水合物中的气体由 99% 的热成因甲烷组成。碳同位素组成 (δ ¹³ (С–С ₁)) 在沉积物中甲烷的范围为 –48.1 至 –48.8‰，水合物中甲烷的范围为 –49.4 至 –50.2‰。油不排放到水柱中。油中未发现 N-烷烃和类异戊二烯；多环芳烃的检测浓度为 1800–2200 ppm，包括 50–90 ppm 的聚苯乙烯和 120–140 ppm 的苝。苝浓度表明石油在其从源头的迁移路径上经历了重大转变。石油中聚苯醚的存在表明其起源于大陆，生物标志物藿烷表明其与贝加尔湖的环烷烃-芳香油相同。贝加尔盆地中部深水区较早新生代沉积物属于有机质来源。