鄂尔多斯盆地延长组长7期湖盆古生产力恢复及其控制因素

发布时间：2018-05-01 15:34

本文选题：鄂尔多斯盆地 + 延长组　；参考：《西北大学》2015年硕士论文

【摘要】：“富烃凹陷”目前已成为我国油气领域研究的热点,优质烃源岩作为富烃凹陷形成的物质基础,尤为被重视。大量的研究表明,优质烃源岩的形成与高的古生产力和有机质的良好保存密切相关,且相比较而言古生产力更为重要,为此,古生产力的研究,对进一步探讨优质烃源岩形成机理及富烃凹陷的形成环境有着重要的意义。鄂尔多斯盆地矿产资源丰富,油气资源量巨大,其与延长组富烃凹陷的存在有着十分紧密的关系。本论文以天环坳陷北部盐56井及盆地南部露头剖面为重点研究对象,开展了有机碳、密度、孔隙度、饱和烃色谱和孢粉化石等测试分析,并结合测井资料计算有机碳的方法,对延长组优质烃源岩形成时期湖盆的古生产力进行定性评价和定量恢复；根据孢粉测试结果对当时的古气候条件进行了分析和恢复；并结合该期地质事件沉积产物的地球化学特征,探讨古生产力的控制因素及其对优质烃源岩形成的影响。以有机碳含量为指标,采取实验测试和测井计算两种方法对古生产力进行了定性评价,研究表明两种方法所获得的有机碳数值吻合度较高,古生产力评价结果一致,说明测井计算方法在该地区具有良好的应用前景；以此为基础,选取合适的联井剖面,根据测井资料计算有机碳含量的方法,分析了有机碳含量横向演变特征。论文首次对长7优质烃源岩发育期湖盆古生产力进行了定量计算,结果表明,定性评价与定量计算之间结论一致,认为延长组优质烃源岩发育期湖盆古生产力较高,与国内其它地区相比,明显高出许多。根据定量计算的结果,结合前人划分的湖泊营养类型,对该期湖泊营养类型进行了划分。以实验测试数据及测井计算的数据为基础,分析研究了长73优质烃源岩有机碳平面展布特征和长73时期湖盆古生产力分布特征。结合凝灰岩沉积、底部热液流体活动及放射性异常等已有研究成果,研究这些事件性沉积产物与古生产力的空间分布特征,研究结果表明,以上三者与古生产力在平面展布上有良好的空间对应关系；并根据事件沉积产物的地球化学分析结果,探讨其对古生产力形成的作用,进一步讨论其对优质烃源岩形成的影响。综合研究认为,延长组长7段优质烃源岩发育时期,湖盆具有较高的古生产力,湖泊营养类型为富养-超养型,该期高古生产力的形成,是当时湖盆可容空间较大、气候适宜、地质事件广泛发育等因素综合影响的结果。这些因素为当时水体生物的生长提供广阔的空间、适宜的气候条件、能量和营养物质等,促使该期存在一次生物勃发事件,进而形成较高的古生产力,为优质烃源岩的形成提供充足的物质基础。
[Abstract]:"hydrocarbon rich sag" has become a hot spot in the field of oil and gas in China, and high quality source rock, as the material foundation of hydrocarbon rich sag, has been paid more attention to. A large number of studies have shown that the formation of high quality source rocks is closely related to the high paleoproductivity and the good preservation of organic matter, and that paleoproductivity is more important than paleoproductivity. It is of great significance to further study the formation mechanism of high quality source rock and the forming environment of hydrocarbon rich sag. The Ordos Basin is rich in mineral resources and huge in oil and gas resources, which is closely related to the existence of hydrocarbon rich depression in Yanchang formation. In this paper, taking Yan-56 well in the northern Tianhuan depression and outcrop section in the southern part of the basin as the main research object, the organic carbon, density, porosity, saturated hydrocarbon chromatography and sporopollen fossils are tested and analyzed, and the method of calculating organic carbon is combined with the log data. The paleoproductivity of lacustrine basin during the formation of high quality hydrocarbon source rocks in Yanchang formation was qualitatively evaluated and quantitatively restored, and the paleoclimate conditions at that time were analyzed and restored according to the results of sporopollen test. Combined with the geochemical characteristics of sedimentary products of the geological events in this period, the controlling factors of paleoproductivity and their influence on the formation of high quality source rocks are discussed. Taking organic carbon content as index, two methods of experimental test and logging calculation were used to evaluate the paleoproductivity qualitatively. The results showed that the numerical agreement of organic carbon obtained by the two methods was high, and the results of paleoproductivity evaluation were consistent. It is shown that the well logging calculation method has a good application prospect in this area, and on this basis, the transverse evolution characteristics of organic carbon content are analyzed according to the method of calculating organic carbon content according to logging data. In this paper, the paleoproductivity of lacustrine basin during the development period of Chang7 high quality source rock is calculated for the first time. The results show that the conclusion between qualitative evaluation and quantitative calculation is in agreement with the conclusion that the paleoproductivity of lake basin during the development period of high quality source rock of Yanchang formation is higher. Compared with other parts of the country, it is much higher. According to the results of quantitative calculation, the nutrient types of lakes in this period were divided according to the nutrient types of lakes. Based on the experimental data and well logging data, the distribution characteristics of organic carbon in Chang73 high quality source rock and paleoproductivity distribution in Chang73 lacustrine basin were analyzed and studied. Combined with the existing research results of tuff deposition, hydrothermal fluid activity at the bottom and radioactive anomalies, the spatial distribution characteristics of these eventful sedimentary products and paleoproductivity are studied. The above three have a good spatial correspondence with paleoproductivity on the plane distribution, and based on the geochemical analysis results of the event sedimentary products, the effect on the formation of paleoproductivity is discussed, and the influence on the formation of high-quality source rocks is further discussed. The comprehensive study shows that the lake basin has high paleoproductivity during the period of the development of high quality hydrocarbon source rocks in member 7 of Yanchang formation, and the nutrient type of the lake is rich and hypertrophic. The formation of high paleoproductivity in this period is due to the large space of the lake basin and the suitable climate at that time. The result of comprehensive influence of factors such as extensive development of geological events. These factors provided broad space for the growth of organisms in the water body at that time, suitable climatic conditions, energy and nutrients, etc., which contributed to the existence of a biological boom event in that period, and thus formed a relatively high paleoproductivity. It provides sufficient material basis for the formation of high quality source rock.
【学位授予单位】：西北大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：P618.13

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