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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.
In view of the high maturity of marine marine source rocks and the particularity of hydrocarbon source contrast, taking the Paleozoic-Mesozoic in northeastern Sichuan as the research object, the characteristics of rare earth elements in organic matter (kerogen and bitumen) The origin of rare earth elements in organic matter was discussed. According to the statistic analysis of rare earth elements and organic carbon isotopes, the oil source of ancient reservoirs was distinguished, which provided a new method for the comparison of oil sources in areas of high maturity The results show that the total REEs of organic matter in the study area range from 0.23 to 603.39μg / g, which is larger than the host environment. The δEu range of kerogen varies from 0.71 to 1.06, which is lower than that of whole rock, mainly reflecting the deposition of organic matter Reducing environment. The light and heavy rare earth elements ratio of kerogen ranged from 1.01 to 16.73. Compared with that of the whole rock, heavy kerogen enriched from old strata to new strata, the trend of enrichment was at a higher level than that of organic carbon isotope Obvious negative correlation, indicating that rare earth elements in organic matter inherited mainly from the original organic matter can be used as an indicator of organic matter source.Comprehensive comparison of mathematical analysis shows that the main area of the Upper Sinian paleo-oil reservoir The source rocks are Lower Cambrian, and the main source rocks of Upper Permian-Lower Triassic reservoir are Upper Permian and Upper Ordovician.