Diagenesis characteristics and diagenetic facies of tight oil reservoir in Fuyu oil layer of 4th Quantou Formation in Putaohua Oilfield,North Songliao Basin
To clarify the distribution of relatively high-quality reservoirs in Fuyu oil layer of Putaohua Oilfield,a comprehensive study was conducted based on cast thin sections,scanning electron microscopy,nuclear magnetic resonance,and micro-CT analyses.This study involved the characterization of tight oil reservoir features and diagenetic processes,followed by quantitative diagenetic facies division.The results indicate that:①Fuyu oil layer is predominantly characterized by residual intergranular pores and intercrystalline micropores,with intra-granular dissolution pores and intergranular dissolution pores being secondary.Pore and throat radii range from 0.82 μm to 39.42 μm and 0.02 μm to 1.28 μm,respectively,with averages of 4.96 μm and 0.68 μm,classifying them as micro-nano pores+nano throats.②Fuyu oil layer exhibits high visual compaction rates and cementation rates of up to 56％and 35％,respectively.Intense mechanical compaction,along with early calcite and illite infillings that obstruct intergranular pores and throats,are key factors leading to reservoir densification.③Chlorite coatings mitigate compaction intensity and preserve some primary pores,while acidic dissolution of feldspar and volcanic rock clasts forms various types of secondary pores,which are crucial for the formation of relatively superior reservoirs.④Through Q-type clustering of multiple diagenetic intensity parameters,Fuyu oil layer is classified into four diagenetic facies.The weakly cemented,strongly leached secondary pore facies and the weakly compacted,strongly leached residual intergranular pore facies exhibit favorable properties and high oil production in testing,representing the advantageous reservoir types within Fuyu oil layer.
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维普
