The Study Of Sequence Stratigraphy And Sedimentary Facies Of Lower Cambrian Qingxudong Formation In SoutheasternSichuan

On the basis of the comprehensive analysis of previous data,as well as making full use of field measured sections and drilling data,this paper analyzes the lithological section structure,Sedimentary facies and Sequence analysis of outcrops and drilling profiles,understanding of stratigraphic overlapping patterns and key Sequence under the guidance of modern theories of sedimentology and Sequence stratigraphy and other multidisciplinary theories,combined with test and analysis data,field research and indoor analysis,macroscopic observation and microscopic testing combined with the study of Sequence stratigraphy-Sequence stratigraphy-Sedimentary Facies-Sedimentary facies model,the stratigraphic framework of the Qingxudong Formation in the Lower Cambrian is established.The Sequence stratigraphy and Sedimentary facies of the Lower Cambrian Qingxudong Formation in the southeastern part of Sichuan Province are studied by studying the regularity of stratigraphic development and the orderliness of its spatial distribution,sedimentary microfacies and its developmental characteristics in the Sequence stratigraphic framework.In this study,nine wells,including Hi-tech 1 well,Lin 1 well,Dingshan 1 well and Gongshen-1 well,and three field sections of Jinshayan pore,Order,four levels of Sequence.Based on the lithological profile structure,Sedimentary facies and phase Sequence analysis of outcrop and drilling profile,understanding of stratigraphic superimposition pattern and key Sequence stratigraphic search,the Qingxudong Formation is divided into main development and preservation of transgressive systems tract and high The two third-order sequences of the water level system domain are respectively called SQ1 and SQ2 in the lower part of the Qingxuitong Formation from bottom to top.By means of rock type,structure and assemblage characteristics,well logging curves are used to divide the Qingxudong Formation into 6 fourth-order sequences,of which the upper and lower third-order Sequences consist of 3 fourth-order sequences.Further,through the control of key interfaces and the control of high frequency sequences by low frequency sequences,the sequence comparison of the third and fourth levels of the Qingxuitong Formation in the area was carried out,and the third-level sequence and high-frequency sequence stratigraphic framework.Based on the large number of field profiles and the laboratory studies of the Qingxudong Formation in the southeastern part of Sichuan Province,based on the study on the sign of Sedimentary facies and on the basis of rock color types and assemblages,Sedimentary structures,profile features and well logging data,The result shows that the Qingxudong Formation in the study area is a carbonate platform.The main development within the gentle slope and shallow gentle slope.The gentle slope can be subdivided into four types of subfacies: tidal flat,lagoon,shallow bank and microbial mound(reef)at the edge of gentle slope type.The shallow gentle slope subdivides two types of subfacies: shoal and intertidal sea.On the whole,in the vertical direction,the gentle gentle slope gradually evolved from shallow gentle slope to lower slope in the vertical direction;in the plane,inner gentle slope and shallow gentle slope developed in turn from northwest to south east.In the late Early Cambrian seawater receded from northwest to southeast,and the basin sloped from northwest to southeast.Based on the analysis of the distribution characteristics of lithofacies palaeogeography and the evolution of Sedimentary facies along with the evolution of sea level fluctuation in the ?1q1 and ?1q2 sedimentary periods and the regional geological characteristics and sedimentary background of the whole southeastern Sichuan area,The Sedimentary facies pattern of the upper and lower sections of the group.Comprehensive analysis of comparative analysis shows that the study area of the Qing Dynasty in the Early Cambrian basically showed a low paleogeographic landscape in the southeastern Northwest China.The spatial distribution of Sedimentary facies conforms to the gentle slope sedimentary model.From the northwest to the east,the inner gentle slope and shallow gentle slope,The Sedimentary facies belonged roughly to the NE-SW distribution.In the study area of southeastern Sichuan,the sedimentary gypsum salt lake,Gaoyunping and microbial mound-shoal deposits are the main deposits in the study area.In general,the mound and shoal can be superimposed on the plane and in the section,indicating a relatively good reservoir development site located in the southern part of the study area.