Study On The Sedimentary Microfacies Of The Third Member Of Paleogene Funing Formation In Jinhu Depression

The third member of Funing Formation of the Jinhu depression is an important target for exploration in the Subei Basin.Its lithology is mainly a thin interbedded sandstone and mudstone,and the depression has a high degree of exploration.Most conventional traps have been discovered,and a deeper study of the sedimentary system is needed.A breakthrough was made in the prediction of hidden sand bodies.The study used petrology,sedimentology and the theory of "Sedimentary Dynamics of The Windfield-Source-Basin System" as a guide to deepen the sedimentary system research of the third member of Funing Formation of the Jinghu depression.Analyze the sedimentary microfacies,sedimentary development characteristics,spreading rules,and control factors,establish sedimentary models,recover ancient water depth,paleogeomorphology,paleoenvironment,and paleophysical sources,and define the control of various factors on the development of beach-bar sand bodies.The main results and understanding of this study are as follows:1.Based on the observations of the actually core obtained from the third member of Funing Formation of the Jinghu depression,combined with the data of the logging data,the structural characteristics,and the information of the rock sheet,etc.,three major sedimentary systems were identified in the Jinhu depression: : Large-scale constructive delta depositional system in the Jinhu West Depression,sedimentary system of the reformed beach-bar near the Jinhu East depression,and storm sedimentary system in the central deep-water-zone.2.The Jinhu West Depression develops large-scale constructive deltaic deposits.Its source mainly comes from the Zhangbaling uplift in the west.The deltaic sedimentary system is subdivided into sedimentary microfacies,such as subaqueous distributary channel,mouth bar,distal bar.3.According to the genesis,the beach-bar sand body in the Jinhu East depression is divided into normal wind-wave sand-bar and storm-wind-wave sand-bar.The normal sand storm dam is mainly developed in the bottom third section,and the storm-wave sand-bar is mainly developed in the upper part of the second section.The top part of the first section is mainly developed normal wind-wave sand-bar.4.Calculating the ancient water depth during the third member of Funing Formation the Jinhu Depression using the wave trace method and the sandbody thickness method.Use the impression method to restore the paleogeomorphic features.Use the beach direction and paleoclimatic recovery to restore the paleo-wind direction of the the third member of Funing Formation.The calculation method of body thickness calculates the size of the ancient wind,and uses the existing sheet data to observe and describe the source direction of the ancient material.5.Based on ancient water depth,ancient landforms,ancient wind fields and the restoration of ancient sources,it can be seen that the gentle paleo-geomorphology provides favorable terrain conditions for the formation of beach-bar deposits,and the appropriate water depth controls the development of waves.The fourth-eighth level southwesterly wind has transformed the ancient source of the Jianhu uplift.The formation of the beach-bar deposit system in the eastern sag of Jinhu is a typical product of the sedimentary dynamics of the "Sedimentary Dynamics of The Windfield-Source-Basin System".