苏北盆地高邮凹陷古近系阜宁组二段页岩油富集主控因素OA北大核心CSTPCD

The second member of the Paleogene Funing Formation in the Gaoyou Sag is a key area for shale oil exploration within the Subei Basin.The successful implementation of eight horizontal shale oil wells evidences its significant potential and promising prospects of exploration.Addressing challenges such as variations in well productivity and unclear understanding of the main controlling factors of shale oil enrichment,this study utilized core data,logging data,analysis testing data,and production dynamics to investigate the geological characteris-tics and main controlling factors of shale oil enrichment in the second member of the Funing Formation.The results reveal that the mudstone and shale in this member predominantly consist of felsic-argillaceous mixed rocks and felsic-calcilutite/dolomitic mixed rocks,with moderate organic matter abundance and mainly Type Ⅰ and Type Ⅱ1 organic matter.From bottom to top,the organic matter type gradually transitions from humus to sapropelic,with an overall increase in organic matter abundance,providing favorable conditions for shale oil formation.A comprehensive evaluation of lithofacies,oil generation potential,oil content,reservoir characteristics,and compressibility identified three favorable exploration layers in the second member of the Funing Formation:Ⅴ-4 to Ⅴ-9,Ⅳ-2 to Ⅳ-7,and Ⅱ to Ⅲ.Shale oil enrichment in the second member of the Funing Formation is characterized by the following factors:(1)Favorable lithofacies combinations,particularly mixed rocks interbedded with dolomite bands,form the material basis for shale oil enrichment,resulting in high shale oil productivity.(2)A complex pore and fracture system is central to shale oil enrichment,with laminar fractures and cracks serving as the main pathways for shale oil flow,effectively connecting matrix pores and enhancing shale oil conductivity.(3)Higher maturity and favorable preservation conditions are crucial for high and stable shale oil production,with vitrinite reflectance(Ro)between 0.8％and 0.9％,indicating relatively higher retained oil content.Wells located away from long-term active faults exhibit relatively higher free hydrocarbon(S1)content.