Reservoir Characteristics And Main Controlling Factors Of Jurassic Yan'an Formation In Wuqi-Ansai Area

The Jurassic Yan'an formation in Wuqi Ansai area of Ordos Basin is the main oil producing layer in this area.The distribution characteristics of reservoir characteristics are unclear,and the main controlling factors of reservoir are unclear,which seriously restricts the progress of exploration and development in this area.According to the drilling and logging data in the area,combined with core observation and analysis test data analysis,this paper systematically studies the structure,sedimentary facies,paleogeomorphology and reservoir characteristics of the Jurassic Yan'an formation.On this basis,it systematically summarizes the reservoir characteristics and its main controlling factors.At the same time,it develops favorable prediction of the stratification position.The research results provide geological basis for increasing reserves and production of the oilfield.The results show that the thickness of yan10 layer changes greatly from southwest to northeast,and the thickness of yan9 and yan8 layers is relatively stable;The overall structure in the area is high in the East and low in the west,and there is no fault.There are 7 rows of nearly East-West nose structures with good inheritance from bottom to top;There are four paleogeomorphic units in the area: paleo River,paleo terrace,inter river hill and paleo slope;The main sedimentary microfacies are channel microfacies,natural dyke and floodplain.The delta plain subfacies are yan8 and yan9,and three microfacies are identified: distributary channel,inter distributary depression and natural dyke;The sand bodies of yan10 oil layer group are thick and distributed in continuous slices,while yan9 and yan8 are controlled by sedimentary microfacies and distributed in strips;The reservoir in this area belongs to medium porosity and low permeability reservoir;The oil reservoirs are vertically distributed in Yan 8,Yan 9 and Yan 10 oil layers of Yan'an formation,and Yan 9 oil layer group is the most abundant;The main reservoir types are structural lithologic reservoir and lithologic reservoir.Oil and gas accumulation is controlled by structure,sandbody,sedimentary facies and paleogeomorphology.The Jurassic system has a tree like reservoir forming model,in which the hidden fault is the trunk,the paleo river sandbody is the branch,the low amplitude structure is the leaf,and the cap rock is distributed as the crown;A total of19 favorable target areas of class ?,? and ? were screened.