Study On The Single Sand Body Configuration Of The Chang 3 Reservoir In Z73 Area

The Chang 3 reservoir of Z73 area is located in the southwest of the Yishan slope in the Ordos Basin.Due to its characteristics of low porosity,low permeability,and strong heterogeneity,there are many high water-cut wells in the whole area,the problem of high pressure and under injection is serious,and complex distribution of residual oil in the reservoir have become serious problems after more than 10 years of injection-production development,which have affected the efficient development of the reservoir.In this paper,the Chang 3 oil layer group in Z73 area of Ordos Basin is taken as the main research object.On the basis of core data,combined with the results of stratigraphic division,based on the seven-level single sand body standard,the single sand body of the oil layer group in the study area is studied in detail from the aspects of sedimentary characteristics,sand body distribution characteristics and single sand body contact relationship.On this basis,the reservoir characteristics such as petrological characteristics,reservoir space characteristics,physical properties,single sand body reservoir heterogeneity and fracture development characteristics are studied,and their influence on development effect is analyzed.Finally,the injection-production correspondence of single sand body and the plane and vertical distribution characteristics of remaining oil in single sand body are studied,and the measures to improve the injection-production correspondence and the utilization of remaining oil are put forward.The results show that the Chang 3 reservoir group in the study area belongs to delta front deposition.,which develops sedimentary microfacies such as subaqueous distributary channels,channel margins,and interdistributary bays.It is distributed from north/northeast to south,with the favorable facies belt being the sedimentation of subaqueous distributary channels.The main rock type of the reservoir is feldspathic litharenite,and the content of filler is between 7%and36.2%.The main type of pore is intergranular pore,with an average of 5.1%,followed by feldspar dissolution pore.The overall physical properties of the reservoir are low porosity and permeability,and there is significant variation in the physical properties among individual sand bodies.Among them,the physical properties of Chang 3₁^1-2-2,Chang 3₁^2-1-1,and Chang 3₁^2-2-1are relatively better.The reservoir is heterogeneous,with well-developed fractures mainly in the northeast direction.After the single sand layer is refined,the phenomenon of injection-production layer mismatch in the well group is widespread.Among them,the injection-production mismatch of Chang 3₁^1-2-1and Chang 3₁^1-2-2 accounts for about 45%.The main distribution layers of residual oil vertically in the study area are Chang 3₁² and Chang 3₁³layers,with residual geological reserves of 1611.67×10⁴t,accounting for about 82%of the total residual reserve.The distribution of residual oil in each individual sand layer is relatively abundant,and locally connected in patches.The distribution of residual oil is mainly affected by sedimentary microfacies,the contact relationship between individual sand bodies,and the inconsistent injection and production layers.Based on this,measures such as hole filling,peak or finger-shaped water injection well profile control,acidizing and increasing injection of water injection wells without water absorption or weak water absorption are proposed for wells with good sand body connectivity,large oil thickness and abundant residual oil,so as to improve the effectiveness of oil wells and the utilization of residual oil,and lay a good foundation for stable production in the study area.