The Analysis Of Sedimentary Facies And Reservoir Of The Main Outcrop Section Jurassic Yan'an Formation In The Ordos Basin

The Ordos Babsin is a large multu-cycle superimposed basin in China.The oil and gas resourves in the basin are abundant,and the Jurassic Yan'an Formation is the main oil production layer.Although the former studied the sedimentary facies of the Yan'an Formation,it was limited to a small area or using the data of the wells in the basin for research.It lacked the control of the development and distribution of sedimentary relative reservior sands from the macroscopic scale of large areas.Therfore,this paper makes full use of the measured data of the Yan'an Formation field profile to carry out sedimentary facies research,and then to clarify the sedimentary reservior type,developmental facies blet and distribution law,in order to lay a solid foundation to predict the favorable oil and gas zone and favorable reservoir evaluation of the Yan'an Formation in the Ordos Basin.On the basis of fully understanding the research results of the predecessors and the regional geological background data,this paper selects the Lingwu Shigouyi Section,the Yan'an Xinxingzihe Section and the Shenmu Kaokaowusugou Section through the exploration of the Jurassic field profile in the basin.Measured to obtain relevant data such as stratum thickness,stratum lithology,sedimentary structure and paleontology.Through the analysis of the outcrop data,the Yan'an Formation is divided into stratigraphic dividions,and the Yan'an Formation stratigraphic division scheme is fetermined.The Yan'an Formation is divided Yan 1 to Yan 10 oil layer groups from the bottom to the top,and a stratigraphic contrast grid is established.On the basis of stratigraphic division and comparison,sedimentary facies analysis marks,including petrological features,sedimentary structures,paleontology and geochemical data,were used to analyze the sedimentary facies of the Yan'an Formation in the field outcrop section.The three sedimentary facies of river facies,delta facies and lacustrine facies,the characteristics of different sedimentary facies are summarized,and the sedimentary subfacies and sedimentary microfacies of rivers and delta facies are divided.The lateral distribution of sedimentary facies in discussed.The sedimentary phase mode of the Yan'an Formation in the study area is summarized.Combined with sedimentary facies analysis results and reservior petrological characteristics,pro type characteristics and reservior physical properties in different reservoir facies,different types of reservoirs and reservoir development facies are analyzed and evaluated.The I reservoir of the river sand dam in the study area accounts 60%,the II reservoir accounts for 30%,and the III reservoir accounts for only 10% in the river sand dam in the study area.It is considered that the sedimentary microfacie is the best favorable reservoir facie;The II reservoir in the channel sedimentary microfacie accounts for 70.6%,and the III reservoir accounts for 29.4%,which is the favorable reservoir facies belt.There are no I and II reservoirs in the branch flow bay and the breach channel,the III reservoir accounts for only 20%,and the IV reservoir accounts for 80%,which is the unfavorable reservoir facies belt.