Depositional Facies Of The Quaternary In Sanhu And East Cha Er’han Areas Of Qaidam Basin

Qaidam basin is one of the most important oil-bearing basins in the northwest China. Begun to be explored in 1954, the north and west areas of Qaidam basin are mainly sections that exploit oil and gas so that the degree of exploration is very high in these areas, but in the Sanhu and East Cha Er’han areas of Qaidam Basin, the degree of exploration is very low. And it hampers the regional exploration and development. In a word, to resolve the problem of lithologic traps identification of the Quaternary sediment in Sanhu and the east Cha Er’han areas, it is necessary to research the in the facies type, distribution and evolution laws of the Quaternary .Aiming at the geology characteristics and existing data of the research area, integrating geology and geophysics,the observation and description of outcrop and drilling core, the paper studies sedimentary facies types and its space distribution laws of the Quaternary sediment in Sanhu and the east Cha Er’han areas comprehensively, and recover its sedimentary evolution history. And then it shows the development model of sedimentary facies.Firstly, based on the observation and description of a large number of drilling cores in macroscopic and microcosmic aspects, facies marks are summarized, which supplied from the characteristics of lithology, distribution of grain size, sedimentary structure, ichnology and logging facies. These provide powerful evidence for the identification and division of sedimentary facies.Secondly, through the identification of facies marks, sedimentary facies analysis of single well and the analysis of cross sections which can reflect the longitudinal evolution of sedimentary facies, alluvial fan, fan delta, delta and lake facies have been developed in research area. Various sedimentary facies distribute in space regularly. A large number of fan deltas and alluvial fans develop in the south slope. Alluvial plain develops in Ya Ba’er and Quanji areas. Delta distributes in Yanhu and Cha Er’han areas and in other place, lake develops. Every facies and subfacies are divided into various microfacies. Thirdly, based on the study of cross sections, the paper studies and contrasts several cross sections of sedimentary facies and sets up the sedimentary framework in the area. According to the principal and method of sedimentary facies diagrams, and the change laws of bed thickness, sandstone thickness and percentage of sandstone, the plane distribution characteristics and longitudinal evolution of the Quaternary sediment in area are summarized.Lastly, based on the study of every research and integrating the tectonic, geology setting, the paper analyzes the sedimentary facies model and the change laws of the development position of shallow-deep lake sediment and the sediment center.