Research On Reservoir Characteristics Of Chang 4+5₂ In G83 Area Of Jiyuan Oilfield

The G83 area of the Jiyuan Oilfield is located in the western part of the northern Shaanxi slope of the Ordos Basin,Chang 4+5₂member of Yanchang reservoir group is the main producing formation.The results show that(1)The Chang 4+5₂reservoir in G83 area of Jiyuan Oilfield is subdivided into Chang 4+5₂^1-1,Chang 4+5₂^1-2,Chang 4+5₂^2-1,Chang 4+5₂^2-2.The main structural form is high in the east and low in the west,with nose-like uplifts developed in some areas.(2)The study area mainly develops delta front subfacies,mainly underwater distributary channel microfacies,underwater natural dike microfacies and interdistributary bay microfacies.,There are underwater distributary channel deposits in the northeast,which meet in the middle of the study area and extend to the southwest.(3)The reservoir is mainly composed of feldspar sandstone and lithic feldspar sandstone,which are medium-porous and ultra-low permeability reservoirs;the type of reservoir space is mainly intergranular pores and dissolved pores-intergranular pores,and the overall pore structure is medium,belonging to small pores and micro-throat type,pore-throat connectivity is medium,with strong heterogeneity.(4)According to various factors such as lithology,porosity and permeability,the reservoirs are divided into three types.The Chang 4+5₂^2-2sand groups is mainly composed of type II reservoirs,which are distributed in a continuous pattern.The Chang 4+5₂^1-1,Chang 4+5₂^1-2,and Chang 4+5₂^2-1non-major sand groups mainly develop type III reservoirs,followed by type II reservoirs,which are difficult to develop.