Log diagenetic facies identification of tight sandstone based on Fisher discriminant method——Taking Chang 8 reservoir in YQ-XC area of Ordos Basin as an example
Log diagenetic facies identification of tight sandstone based on Fisher discriminant method——Taking Chang 8 reservoir in YQ-XC area of Ordos Basin as an example
Diagenetic facies is closely related to reservoir quality.The study of diagenetic facies can provide guidance for the prediction of reservoir"dessert"and provide basis for oil and gas exploration and development.In this paper,the Chang 8 reservoir in YQ-XC area of Ordos Basin is divided into five types of diagenetic facies according to the type of diagenesis and the combination of diagenetic minerals by using physical property analysis test,casting thin section,scanning electron microscope,cathodoluminescence and other experiments,compact compaction facies,unstable component dissolution facies,residual intergranular pore facies,carbonate cementation facies and clay mineral cementation facies.Through cross plot processing of conventional logging data,it is found that different diagenetic facies have different logging responses,but there are many overlaps between different diagenetic facies,so it is not possible to identify different diagenetic facies through cross plot.The Fisher dis-criminant method is used to calculate the plane projection of each sample point and estab-lish the discriminant function of different diagenetic facies.The correct recognition rate of di-agenetic facies can reach 93.9%.The accuracy of this method is verified by comparing with the identification results of cast thin sections.At the same time,combined with the analysis of cuttings logging data,it is considered that diagenesis has a certain control effect on oil and gas enrichment.The reservoir of residual intergranular pore facies is an oil and gas en-richment area,followed by the dissolution facies of unstable components.The residual inter-granular pore facies and the dissolution facies of unstable components can be taken as the key areas for the next oil and gas exploration and development in the study area.
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