Description Of Chang 2 Reservoir In The Southern Part Of ×× Oil Field

The Chang 2 area in the south of the××oilfield is located in the south of××County,and the development horizon is the Chang 2 oil layer group of Yanchang Formation.The study area covers an area of 189km² and the total number of oil and water wells is 2,480.The geological conditions in this area are complex.The previous understanding was to conduct separate geological research for each small block,and even the stratigraphic division plan was inconsistent.This research is based on the theories of petroleum geology,sedimentary petrology,reservoir geology,logging,structure,etc.,combined with drilling,logging,coring,analysis and testing and other data,systematically study the reservoir characteristics such as stratigraphy,structure,sedimentation,sand body and so on in the study area.The reservoir characteristics of Chang 2 area in the southern part of the××oilfield are studied,and the classification and evaluation are completed at the end to provide theoretical basis for future development of Chang 2 reservoir in oilfield.The research results show that the stratum of the Chang 2 oil layer group in the southern part of the××oilfield can be subdivided into Chang 2^1-1,Chang 2^1-2,Chang 2^1-3,Chang 2^2-1,Chang 2^2-2 and Chang 2³.The thickness is relatively stable.Low-amplitude nose-like structures are developed in each small layer in the study area,and have certain inheritance.The study area belongs to the delta plain subfacies deposits.The main microfacies types include branch channels,land natural dikes and marsh microfacies,and river sand bodies on the plane Large-area superimposed contiguous distribution,large thickness,and good sand body connectivity.The reservoir rock is mainly feldspar sandstone,the interstitial material in the pores is mainly chlorite,followed by calcite cement.Diagenesis is strong,and compaction,cementation and dissolution are common.Dissolution can improve the physical properties of the reservoir.The average porosity of the main oil layers Chang 2^1-3,Chang 2^2-1 and Chang2^2-2 in the study area are 13.71%,14.40%and 14.17%respectively,and the average permeability are 6.75×10^-3μm²,7.20×10^-3μm² and 6.29×10^-3μm² respectively.,due to the influence of diagenesis,the correlation between porosity and permeability is poor.From a plane perspective,the area with better physical properties of Chang 2^1-3 is mainly in the middle of the study area;Chang 2^2-1 is mainly in the middle of the study area,and the east is slightly worse;Chang 2^2-2 is mainly in the middle and east of the study area.The pore types in the study area are mainly intergranular pores,and the pore throat types are large-pore medium-fine throat type and medium-pore medium-fine throat type.The Chang 2 reservoir in the study area has strong heterogeneity and medium sensitivity.It is characterized by moderately weak to weak water sensitivity,moderately weak to weak speed sensitivity,weak to moderately weak salt sensitivity,moderately weak alkali sensitivity and weak acid sensitivity.The Chang 2 in the study area is the most developed type II and III reservoirs,type II accounted for 61.98%,type III accounted for 29.37%,type IV was slightly developed,accounting for 8.65%,and type I was underdeveloped.The oil-rich areas were mainly in II and Class III area.