Deposit System And Sandstone Genesis In Chang 6 Oil-bearing Formation Of Yanchang Formation In Baibao-huachiarea, Ordos Basin

Introduction of the author:Longhao male, was born in April, 1986 whose tutor was Professor Tianjingchun . He graduated from Chengdu University of Technology in Sedimentology major and was granted the Master Degree in June,2011. Based on the previous studis,borehole,well logging data and other analysis,this thesis studies the sedimentary structure , lithology and well logging characteristics with the guidance of sedimentology , sedimentary facies and palaeogeography and sequence stratigraphy, according to which we finally investigate the depositional system and sandstone genesis in Chang 6 oil-bearing Formation of Yanchang Formation in Baibao-Huachi area,Ordos Basin.By analyzing regional tectonic evolution of Yanchang Formation,we consider the lake basin of Chang 6 Formation was developing in a shrinking-filling style.We identifies the lake delta deposit system and lake deposit system in study area by means of lithologic symbols,sedimentary structures,grain size distribution,depositional sequence,paleogene fossils and logging facies.Moreover,we confirm the lake delta is delta-front subfacies while the lake deposit system is half-deep lake to deep lake subfacies.Furthermore,the delta-front subfacies can be divided into subaqueous distributary channel,debouch bar,underwater natural levee,underwater crevasse fan,interdistributary,half-deep to deep lake mud and turbidite microfacies.We have did comprehensive research on the sandstone distribution of Chang 6₁,Chang 6₂, and Chang 6₃,and compliled the lithofacies paleogeography map.Combining the sedimentary symbols,types and characteristics we then establish the sedimentary model for Chang 6 Formation.Genetic types and the characteristics of sandbodies in Chang 6 formation are systematically researched through plenty of core observations and testing data, it can be found that both normal deposits and event deposits exist in Chang 6 formation in Baibao-Huachi area. The sandbodies caused from normal deposit are mainly delta front sandbodies controlled by meanderingriver delta system from northeast, further including underwater distributary channel, mount bar, superpose underwater distributary channel, superpose mount bar and mixed types. The sandbodies resulted from event deposits include earthquake and turbidity current causing superimposed type and the type mixed by event deposit and normal deposit causing sandbodies.