Reservoir Characteristics And Remaining Oil Distribution Of Donghe Sandstone Formation In Tazhong 4 Oilfield

Tazhong 4 oilfield is located in the middle of Taklimakan Desert in Tarim Basin,Xinjiang Uygur Autonomous Region.The target study stratum is Donghe Sandstone Formation in CIII oil group,which is a significant petroliferous reservoir in Tarim Basin,consisted by marine-continental transitional facies glutenite in the bottom and marine massive sandstone in the top,with variation among each layer.This thesis analyzes core test data during the exploration and development of Tazhong 4 oilfield,combining with well log,seisimic and production data,to study the reservoir,seepage barrir and remaining oil characteristics.Detailed study on reservoir characteristics is done in 4 aspects,which are lithology,pore-throat structure,physical property and seepage feature.A reservoir evaluation standard is established according to porosity,permeability,sorting and pore-throat structure parameters to classify reservoir into 4 categorys,8 types: high permeability(high and medium porosity),medium permeability(medium and low porosity),low permeability(medium and low porosity)and extra-low permeability(low and extra-low porosity).Then the affections of sedimentary environment,diagenesis and hydrocarbon on reservoir quality are discussed.The seepage barrier type and distribution features are studied and a dynamic-stastic combined method is used to predict its inter-well distribution pattern.The distribution of important interlayer and the development degree of seepage barrier in each layer is determined.Three types of remaining oil genesis are raised,which are seepage barrier sheltered remaining oil,reservoir variation remaining oil and structural factor remaining oil.The favorable distribution area of each type of remaining oil is concluded at last.