Characteristics And Relationship Of Ultra-low Permeability Reservoirs And Hydrocarbon Accumulation

Based on logging interpretation,scanning electron microscope photos,high-pressure mercury intrusion data,experimental analysis data,drilling and logging data,and useslarge-scale dense well patterns to study the types of sedimentary micro-facies,reservoi r micro-and macro-features in the study area.Analyze and complete the reservoir clas sification and evaluation of the study area,and at the same time analyze and study th e reservoir distribution characteristics.Finally,the multi-factor superimposition method i s used to reveal the control effect of sedimentary microfacies,reservoir types,reservoir physical properties,and reservoir heterogeneity on the distribution of oil reservoirs in the study area.The research results show that the Chang 6 formation in the study area is well d eveloped and the thickness is stable.According to the marker layers and cycle combin ations,the Chang 6 oil layer group can be divided into Chang 6-1,Chang 6-2,Chang 6-3,and Chang 6-4.Each small layer.The Chang 6 oil layer in the study area mainl y develops delta front subfacies,including underwater distributary channel,distributary bay,estuary bar,and remote sand bar.The source direction is generally north,southeas t,west,and distributary channel and estuary bar are the most development.The reserv oirs in the study area are dominated by fine-grained feldspar sandstone,with intergranu lar dissolved pores as the main storage space,low-porosity and ultra-low-permeability r eservoirs with poor physical properties,and strong heterogeneity in each layer.Accordi ng to the characteristics of microstructure,heterogeneity,physical properties,etc.,the re servoirs in the study area can be divided into three types from good to bad.The distri bution range of each sublayer type I,type II,and type III reservoirs is different.Thro ugh the calculation of the effective thickness of the reservoir,the oil saturation,and th e drawing of the plan,the law of oil and gas distribution in each small layer is ascert ained.The area of oil and gas distribution in the study area is large.Except for the s mall area in the northeast of the study area,other areas are large.Area of discontinuo us distribution area.A comprehensive analysis of the above analysis factors reveals that the areas with larger oil saturation values are mainly distributed in the main body of the distributary channel and the main microfacies of the estuary dam.The areas with greater oil saturation are mainly distributed in Type I and Type II reservoirs.Reservoir heterogeneity has a strong controlling effect on oil and gas distribution,and the distri bution of sedimentary rhythm,sand body thickness,and barrier thickness have a contro lling effect on oil and gas distribution.Reservoir physical properties have a strong con trol effect on oil saturation.The oil-bearing thickness saturation is high in areas with good reservoir physical properties,but the relationship with the effective thickness of t he oil layer is not obvious.