Research On The Reservoir Heterogeneity And Pool Characteristics Of Yan9 Oil-bearing In 4914 Wells Area Of Shanbei Dingbian Oil Field

4914 well area of Dingbian oilfield is located in the south of Dingbian oilfield,and tectonic units belong to transitional zone of Yishan slope and Tianhuan depression.The Yan 9reservoirs of Yanan formation is main production layer,which has entered middle exploitation stage.The crude output is high in the early production stage and total water cut is low in the study erea.The reason caused fast production decline and poor water injection effect is that early geological research is relatively weak,especially unclear to reservoir heterogeneity and pool characteristics.To provide the basis for formulating a reasonable plan for the oil field development.This article is guided by the basic theoretical theories and methods of reservoir geology and petroleum geology.Based on analysis of SEM,thin section analysis,mercury pressure and grain grade analysis,combined with cores,drillings,loggings,oil testings and other basic data,a series of studies of Yan 9 formation have been carried,including sedimentary facies and sanding distribution,heterogeneity of reservoir,four properties' relations,oil-water layer identification and resevoir characteristics.Through the above research,the main controlling factors of reservoir enrichment are analyzed.The layer thickness of the Yan 9 formation is about 60m⁷0m in the study area,in which Yan 9¹,Yan 9² are around 20 m and Yan 9^3-1,Yan 9^3-2are about 15 m.The top surface structure of each small layer is similar and show high in the east and low in the west of the study area.There are three rows of north east axial trending low nose structure from the north to the south and the southern nose-shaped uplift is relatively wider.The existence of these uplifts is related to the development of sandstone and the enrichment of reservoir.Yan 9 oil-bearing formation of the Dingbian oil field is belonged to delta plain subfacies depositional system,including distributary channel,natural levee,crevasse splay,flood plain and distributary bay 5 microfacies,and the dominant sedimentary micro facies is distributary channel distributing along the northeast-southwest stripe.Yan 9 reservoir lithology of the study area is mainly grayish white medium grained lithic quartz sandstone.The cementation is mainly kaolinite and calcite.The main pore types include primary intergranular pores,dissolved pores,intergranular pores and microcracks.Yan 9 formation of pore throat is mainly medium pore and coarse throat,which belongs to low pore and low permeability reservoir.The in-layer heterogeneity about Yan 9 reservoir is weak,and the interlayer heterogeneity is strong,but the overall heterogeneity is weak.Yan 9 reservoir lithology lower limit of oiliness is medium sand,and the electrical lower limit are?t?240?s/m,RILD?6.5?·m.The petrophysical lower limt of porosity is 9%and permeability is 6.0mD.The Yan 9 reservoir in the study area belongs to the structural-lithologic combined reservoir,and the hydrocarbon mostly concentrated in Yan 9³ layer.The reservoir distribution is mainly controlled by the distributary channel and the nose-shaped structure.The skeleton sand of distributary channel microfacies controls the reservoir distribution and the nose-shape structure affects the accumulation of the reservoir,and the mudstone of the distributary bay has the upward occlusion.The superimposed zone of distributary channel and nose-shaped structure is the main enrichment zone of reservoir.The reserves estimation shows that the Yan9 reservoir belongs to middle-shallow layer,small-scale,low production conventional small light reservoir.