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塔里木盆地西部中上奥陶统萨尔干组页岩和印干组页岩是古生代重要的烃源岩,该盆地西部中上奥陶统烃源岩的研究对于探寻油气成藏有利区带及指导实际勘探有重要意义。为进一步分析其形成时的环境条件,应用地球化学手段对其进行研究,选取露头上具有代表性的样品对其进行微量元素和稀土元素分析、岩石热解分析和矿物含量分析。结果表明,该烃源岩的微量元素分配模式以U、Nd和Sm富集,Ba和Sr亏损为特征,∑REE介于(80.04～370.2)×10-6范围,LREE/HREE值为10.87～13.99,LaN/YbN值为7.92～11.218,δEu为0.680～0.849,稀土配分模式属轻稀土富集型。有机碳(TOC)含量为0.39%～2.93%,氢指数(HI)为39～122mg/g,说明该烃源岩处于较成熟阶段,尚有一定的生烃潜力。综合该地区萨尔干组页岩与印干组页岩的露头岩性特征、富含笔石与腕足类化石以及黄铁矿发育等特点,结合室内微量元素、稀土元素、岩石热解数据以及X射线衍射定量综合分析,认为阿克苏中上奥陶统地层发育于深水陆棚—盆地沉积环境中。
The Middle-Upper Ordovician Salkan Shale and Yinchuan Shale in western Tarim Basin are the important Paleozoic source rocks. The study of the Upper-Middle Ordovician source rocks in the western part of the basin is of great interest in exploring favorable hydrocarbon accumulation zones and Instructing actual exploration is of great significance. In order to further analyze the environmental conditions during its formation, geochemical methods were used to study the samples. Representative samples from outcrops were selected for trace element and rare earth element analysis, rock pyrolysis analysis and mineral content analysis. The results show that the distribution patterns of trace elements in this source rock are characterized by enrichment of U, Nd and Sm and depletion of Ba and Sr, ΣREE is in the range of (80.04 ~ 370.2) × 10-6, LREE / HREE is 10.87 ~ 13.99, LaN / YbN values of 7.92 ~ 11.218 and δEu of 0.680 ~ 0.849. The REE patterns are light rare earth enrichment. Organic carbon (TOC) was 0.39% -2.93%, and hydrogen index (HI) was 39-122 mg / g, indicating that the source rock is at a relatively mature stage and has a certain potential for hydrocarbon generation. Based on the characteristics of outcrops lithology of the Salkan shale and the Indo-China shale in this area, they are rich in lithosperm and brachiopod fossils and pyrite development. Combining the indoor trace elements, rare earth elements, rock pyrolysis data and X-ray diffraction quantitative analysis, that the Aksu Middle-Upper Ordovician strata developed in the deep-water shelf-basin sedimentary environment.