细粒沉积物层序地层划分方法初探:以东营凹陷樊页1井沙三下-沙四上亚段泥页岩为例

Methods of Sequence Stratigraphy in the Fine-Grained Sediments:A Case from the Upper Fourth Sub-member and the Lower Third Sub-member of the Shahejie Formation in Well Fanye 1 of Dongying Depression

东营凹陷沙三下-沙四上亚段发育了一套厚层的泥页岩,前人研究认为这一套厚层泥岩是经典层序地层学中的湖进体系域(EST),没有做过进一步的细分。随着近年来页岩油(气)研究的深入开展,地质学家们认识到了泥页岩并非整体一套,而是与砂岩一样也具有明显的非均质性,这就要求针对泥页岩等细粒沉积物的研究要进一步精细化。对于泥页岩的层序研究而言,传统(经典)的划分方法完全不适应(依据经典层序地层接触关系、地震反射特征、岩性组合变化等参数),因此迫切需要寻找一种切实可行的方法对泥页岩进行层序精细划分。通过研究,提出了基于T-R旋回理论的GRP层序划分法。该方法以自然伽马曲线(GR)为基础,结合岩相变化分析,充分利用各类地球化学数据以及GR测井在泥页岩层段响应特征和湖平面T-R旋回变化的耦合关系,进行泥页岩中的旋回识别分析。利用该方法,将东营凹陷樊页1井沙三下—沙四上亚段从下至上划分为7个GRP(GR Parasequence)层序,并进一步分析了控制细粒沉积物层序的因素。

In Dongying Depression, the upper fourth sub-member and the lower third sub-member of the Shahejie Formation, containing a thick layer of mudstone and shales, have been regarded as a transgressive systems tract （EST）. In recent years, with the deepening of the research for the unconventional sources, geologists have recognized that the shale like sandstone also has strong heterogeneity. However, the tradi- tional research methods of sequence stratigraphy cannot be directly used to study the mudstone and the shale, thus a new approach must be found to analyse the sequence structure of the fine-grained sediments. This study has thus proposed a GRP sequence classification method based on T-R cycle theory. Based on natural gamma curve （GR） and lithofacies changes, the study analyzed and recognized the cycle changes in mudstone and the shale, using various geochemical data, was analyzed and recognized. With this GRP（GR Parasequence）method, we divided the upper fourth sub-member and the lower third sub-member of the Shahejie Formation into 7 subsequences vertically and analysed the factors controlling the fine-grained sedi- ment sequence.