Study On Remaining Oil Distribution Of Low Permeability Reservoir In The 8^th Member Of Yanchang Formation In Zhen 218 Block,Zhenbei Oilfield

Zhenbei oilfield is located in the southwest of Yishaan Slope,Ordos Basin.The 8th Member of yanchang formation of Triassic is the main oil-bearing series,It is a typical low permeability reservoirs.Zhen 218 block is located in the east of Zhenbei oilfield.Many scholars has done some research on this region,In order to solve the problem whice is existing in this region such as water cut rising rapidly,bad reservoir physical property,stronger heterogeneity,high remaining oil saturation and a complex distribution of remaining oil etc.This paper comprehensively utilizes the data such as geological,Logging,analysis assay and production performance and so on,studying the sedimentary and reservoir characteristic analysis,use logging to calculate the parameters of low permeability reservoir,analysis and evaluation of remaining oil.The following results were achieved:(1)The 8th member of Yanchang formation in Zhen 218 block are braided delta front facies,subaqueous distributary channel,fluvial channel sandstones and subaquatic interdistributary embayments are the main microfacies of chang 81 sub member.By analysis that subaqueous distributary channel are the main microfaices of the 8th Member of Yanchang Formation in Zhen 218 block.(2)The 8th member of Yanchang formation in this region is low porosity and low permeability reservoir,the average permeability and porosity is respectively 1.91×10-3?m2 and8.85%,By introducing heterogeneous synthetic index,reservoir heterogeneity of this region are calculated and characterized quantitatively.It shows this region has moderate to strong heterogeneity.(3)Reservoir parameters are obtained.Base on low permeability reservoirs,setted up the logging interpretation models of porosity,permeability,oil saturation and the discriminant standard of Oil,water,dry layer in the 8th Member of Yanchang Formation in Zhen 218 block.And validation the result of the logging interpretation.Found that the interpretation conclusion compared with the original explanation to the conclusion that core analysislaboratory error reduced almost 27%,fluid producing better matching relation between strength and permeability parameters,test was coincidence rate is 87.5%,Conclusion the logging interpretation is more reasonable.(4)Determine each layer of remaining oil saturation of Chang81 reservoir in Zhen 218 block.And by using reservoir numerical simulation were compared to verify,found out that the conformity degree is higher on the overall,only has difference in the local such as zhen217-20 well.Illustrates the accuracy that utilization of relative permeability and water drive curve method to calculate the remaining oil saturation.(5)By introducing Data Envelopment Analysis to calculate the remaining oil distribution index of every well.According to the numerical size of the I,The level of enrichment of remaining oil in this region can be divided divided into enrichment,the enrichment and secondary enrichment,less enrichment and enrichment.It can be characterization quantitative enrichment of remaining oil in Chang811 in zhen 218-1 block.(6)Chang811 in zhen 218-1 well group and Chang 812 in zhen 218-2 well group are enriched of remaining oil The main influencing factors of remaining oil enrichment are sedimentary,reservoir heterogeneity and development technique.(7)Summarizes the Residual Oil Distribution Law of chang 81 sub member in Zhen 218 block.Four distribution patterns of remaining oil are proposed,the effectiveness of injection-production well pattern is uneven,oil reservoir heterogeneity control pattern,interlayers in thick oil layer pattern,discontinuous oil layers pattern.