苏北盆地高邮凹陷古近系阜二段页岩油富集模式OA

This study was undertaken to address the limited understanding of the primary controls on shale oil enrichment and the challenges in predicting high-quality"sweet spot"intervals within the sec-ond member of the Paleogene Funing Formation(E1f2)in the Gaoyou Sag,Subei Basin.The aims of this paper are to reveal the controlling mechanisms of different lithofacies assemblages on shale oil en-richment and mobility,clarify the characteristics of differential oil-bearing properties in the area,and ul-timately establish an enrichment model to guide exploration deployment.Focusing on the E1f2 shale in the Gaoyou Sag,we comprehensively employed an integrated experimental methodology including core observation,thin-section identification,X-ray diffraction(XRD)mineral analysis,organic geochemical testing,scanning electron microscopy(SEM),low-temperature gas E1f2 adsorption,high-pressure mer-cury intrusion porosimetry(MIP),and nuclear magnetic resonance(NMR).This integrated approach enabled systematic lithofacies classification,pore structure characterization,and evaluation of oil-bear-ing potential and hydrocarbon mobility.Building on this,we focused on analyzing the reservoir proper-ties,hydrocarbon generation potential,oil saturation,and fracturability of different lithofacies assem-blages.The oil-controlling effect of lithofacies assemblages was empirically verified through coupled To-tal Scanning Fluorescence(TSF)and pyrolysis parameter analysis on samples from typical assemblages.The research identifies four main lithofacies in the study area:mixed shale,calcareous-dolomitic shale,felsic shale,and argillaceous shale,which form three dominant assemblages,namely Pure Mixed Shale,Mixed Shale Intercalated with Calcareous-Dolomitic Shale,and Mixed Shale Intercalated with Felsic Shale.Among these,the Mixed Shale Intercalated with Calcareous-Dolomitic Shale assemblage,due to its calcareous-dolomitic interlayers featuring dissolved pores,a trimodal pore structure,excellent pore-throat connectivity,and high brittleness index,exhibits the strongest free hydrocarbon enrichment ca-pacity and mobility,representing the"sweet spot"interval for shale oil enrichment.The mixed shale matrix possesses superior hydrocarbon generation potential but moderate mobility,primarily acting as the hydrocarbon source and in-situ storage unit.The felsic shale,characterized by well-developed micro-pores and high displacement pressure,acts as an effective sealing barrier.This study establishes a conti-nental shale oil enrichment result centered on the concept of"Enrichment dominated by sweet spot inter-layers(Calcareous-Dolomitic Shale),accumulation supported by hydrocarbon-prone matrix(Mixed Shale),and preservation sealed by tight interlayers(Felsic Shale)".This result provides significant the-oretical guidance for shale oil exploration in the Subei Basin and analogous geological settings.