Study On Reservoir Heterogeneity Of The 1st Member Of Qingshankou Formation In Daqingzijing Oilfields In Jilin Province

The Daqingzijing Oilfields in Jilin is located in the southern part of the central depressional zone of the Songliao Basin.After the long-term exploration and development production of the block Hei 70,the difficulties of thin reservoirs,rapid plane changes and non-homogeneity of the main oil reservoir are gradually highlighted and the development is becoming more and more difficult.In this thesis,a section of the block Hei 70 of the Qingshankou Formation in the Daqingzijing Oilfields is selected as the study objective.Based on previous studies on the regional sedimentary system in the southern part of the Songliao Basin,stratigraphic delineation and comparison work is carried out with the data of cores,logs,seismic and analytical assays to further complete the sedimentary microphase carving,complete the reservoir log interpretation using the standardized log data,carve the study area,analyze the reservoir inhomogeneity and discuss its effect on the reservoir.The reservoir non-homogeneity characteristics are analyzed and their controlling effect on the reservoir is discussed,and finally the favorable reservoir distribution is predicted.The study shows that the K₂qn¹ of the block Hei 70 of the Daqingzijing Oilfields can be divided into 4 sections and 16 substrata,which develop shallow water delta frontal subphase deposits.It mainly developing submerged divergent channels,submerged divergent channels interbay,mat sand,estuarine dams and other sedimentary microphases,with submerged divergent channels sand body as the backbone sand body,spreading along the southwest-northeast direction in a strip.The reservoir in the study area as a whole belongs to the low-porosity and ultra-low-permeability reservoir,with mud interlayer and calcareous interlayer developed,the thickness of interlayer is mainly 0.2m-1m,the distribution interval of interlayer frequency and density is 0-0.3,and the 12 small layer interlayer is the most developed.The green section reservoir in the area shows strong permeability inhomogeneity,and the small layers 7,12,14 and 15 are stronger permeability inhomogeneity,and the small layers 1,2,9 and 11 are weaker permeability inhomogeneity.The entropy weight method was used to calculate the comprehensive index of inhomogeneity and analyze the inhomogeneity of 16 minor layers in the green section of the study area.Among them,sub-layers 7,12,14 and 15 show moderate non-homogeneity;sub-layers 9,10and 16 have slightly weaker non-homogeneity and are moderate-strong non-homogeneity;the rest of the sub-layers are strongly non-homogeneous.The distribution of favorable reservoir zones in the study area is mainly influenced by the spreading of sedimentary phase zones and reservoir inhomogeneity,and the favorable reservoir distribution zones are classified into four class（Class I,II,III,IV）.The results show that the distribution of reservoir favorable zones in the study area is mainly in Class II and Class III,and the Class I favorable zone has the best comprehensive quality but also the least distribution,which can be planned as the next target construction area.