The Southwestern Ordos Basin Chang-7 Depositional Environment Of The Fine Grained Sediment Impact Study

In recent years,along with oil and gas exploration and development,process speed up and the rapid progress of science and technology,the domestic and overseas academics studies of terrestrial lacustrine basins has reached a new height.The fine grained sediment research become one of the hotspot contents in the research terrestrial lacustrine basins.There are widely developed fine grained sediments of the chang-7 period in Ordos basin.The paper selects the fine grained sediment of the chang-7 period in Ordos basin as research object which analyzes characteristics and faces of fine grained sedimentsby the core description,thin section observation,geochemical testing;by the trace elements test,the carbon and oxygen isotope composition,geochemical testing,paleontology identification,emphatically analyzes the formation environment of fine grained sediments,combined with fine grained sediment types of the sedimentary facies,analysis of sedimentary environment of the master control factor for the formation of fine grained sediments,and analysis of fine grained sediment distribution characteristics and laws.The study results show that sedimentary facies,lake water properties,water depth,flow is fine grained sediment formation and distribution of main control factor;The fine-grained sedimentary of Chang-7 develops mainly development environment includes: delta front,front delta,gravity flow,semi deep lake and deep lake sedimentary environment;The paleowaters of chang-7 basically maintained the fresh terrestrial lacustrine environment.The water depth of the range is 0-200 m,the largest depth is 100-200 m.The climate is warm and humid climate.The chang-73 is brown shale gas,only in the northeast developed fine sandstone.The chang-72 is brown Mudstone and sandstone.Shale in central lake basin began to decrease relatively,has formed sandy clastic current deposits of fine sandstone;The chang-71 fine sandstone main development in the northeast and southwest,central lake basin is given priority to with sandy debris flow deposits of fine sandstone,relatively the chang-72,relative to expand;Tuff mainly developed in the center of the basin in the south east to Hua Chi-XunYi area,the distribution of the center of the lake basin north west tuff is less,the overall shape in the north west to distribution,from southwest to north east tuff thickness thinning.