湖相泥页岩层系无机非均质性成因机理及其地质意义

Genetic mechanisms of heterogeneity in shale formation is the research basis of occurrence mechanisms and reservoir property. A clear understanding of the characteristic and genetic mechanisms of heterogeneity will help us to establish the prediction mode of oil and gas bearing property in organic-rich shale system, and make a foundation for shale oil resource evaluation. This application use the continuous coring well of Paleogene Shahejie formation in Jiyang Depression as the research target, describing the heterogeneity in details. Discussing the genetic mechanisms of heterogeneity with sedimentation, diagenesis and late reformation respectively. Establishing the relativities between the lithologic heterogeneity and logging parameters. According to the variation characteristic of element in XRF test, process the XRF data with different method. Based on the identification of lithology by the distribution of elements, establish the prediction method of inorganic heterogeneity in lacustrine shale formation which is based on the logging technology, and apply it in other research area, which will providing new parameters to the identification of lithology and lithofacies in shale formation.

泥页岩层系的非均质性成因机理是其储集性能与页岩油赋存机理研究的基础，只有明确泥页岩非均质性特征及成因机理，才能建立富有机质页岩含油气性的预测模式，为页岩油资源评价奠定基础。本申请以济阳坳陷古近系沙河街组系统取心井段为主要研究对象，对其非均质性特征进行系统分析；分别从沉积作用，成岩过程及后期改造三个方面，探讨泥页岩无机非均质性的成因机理；建立岩性非均质性与测井参数的对比关系，根据XRF测试井段页岩元素变化特征，对XRF测试数据点进行数据处理，同时以元素分布特征识别岩性为基础，建立基于测井技术的湖相泥页岩层系无机非均质性预测方法，并在研究区内进行地质应用，为泥页岩层系岩性与岩相识别提供新的预测参数。

与北美海相页岩相比，中国陆相湖盆泥页岩具有分布范围小，沉积相变快的明显差异，表现出很强的岩石组构和化学组成非均质性。因此如何有效的刻画这种多重地质因素影响下导致的无机非均质性，成为当前非常规油气储层有利区预测的关键问题之一。本项目综合运用元素地球化学、岩石物理等研究手段，以济阳坳陷沙三、沙四段层段泥页岩系统岩心为主要研究对象，开展高密度岩矿分析。通过大量的基础实验分析，建立了高效的无机非均质性刻画方法和技术流程。通过系统研究工作明确了济阳坳陷沙河街组泥页岩层系具有块状泥岩、页岩、纹层~层状灰质泥岩、纹层~层状泥质灰岩和粉砂质泥岩等五大类岩性类型，并结合测井参数，建立了上述矿物与测井曲线之间的数学关系和预测模型。通过元素地球化学的分析结果，认为沙四上亚段至沙三下亚段泥页岩层系经历了两次湖平面的升降旋回，整体上气候从炎热变湿润，水体盐度降低，揭示了从沙四上到沙三下亚段泥页岩中的陆源碎屑输入增加、碳酸盐岩含量逐渐降低和岩性频繁变化等造成泥页岩非均质性的环境因素。针对泥页岩中石英和碳酸盐岩矿物的成因机理开展了探索，发现这里泥页岩中的石英主要来源于陆源碎屑，而纹层和细脉状碳酸盐岩主要为成岩作用晚期随着有机的热演化经过溶解和再沉淀作用的产物。