苏北盆地高邮凹陷古近系陆相页岩油勘探突破及意义

Breakthrough and significance of Paleogene continental shale oil exploration in Gaoyou sag,Subei Basin

2022年,苏北盆地高邮凹陷针对古近系阜宁组二段(阜二段)实施了两口重点页岩油探井--HY1HF井和H2CHF井,压裂后在排采阶段分别获得29.7 t/d和50.5 t/d的工业油流,实现了高邮凹陷阜二段页岩油勘探的重大突破。综合来自HY1井等的岩心和岩石薄片观察以及X射线衍射全岩矿物、氮气吸附、核磁共振、冷冻岩心有机地球化学分析等实验资料,结合HY1HF井、H2CHF井等井的生产动态数据,系统分析了高邮凹陷阜二段页岩的地质特征,进一步揭示了苏北盆地阜二段页岩油的富集规律及控制因素。高邮凹陷阜二段发育半深湖—深湖亚相泥页岩,具有纵向厚度大、平面分布广的特征,是其页岩油富集的基础。页岩的岩相控制着"生油甜点"和"储集甜点"在平面上和纵向上的分布,其中,黏土矿物含量相对较高的岩相具有较好的生烃潜力,长英质矿物、碳酸盐矿物含量较高的岩相表现出具有较好的物性和孔喉结构。根据岩性组合特征,阜二段页岩油藏可划分为"自生自储"型、"泥生灰/云储"型和"泥生砂纹储"型。"泥生灰/云储"型页岩油藏的源-储组合中发育优质孔-缝体系,具有含油性好和流动性高的特点,且已有的生产动态资料表明,这类页岩油藏具有较好的页岩油产能。良好的保存条件和页岩加熟生烃增压是页岩油高产、稳产的关键。高邮凹陷阜二段页岩油的勘探突破表明苏北盆地古近系页岩油具有良好的勘探前景,高邮凹陷是增储上产的重点领域。该研究成果对于中国东部陆相断陷盆地页岩油的勘探开发具有重要的借鉴与指导意义。

In 2022,two key shale oil wells(Well HY1HF and Well H2CHF)were explored for Member 2 of Paleogene Funing Formation in Gaoyou sag of Subei Basin,and an industrial oil flow of 29.7 t/d and 50.5 t/d was separately obtained after fracturing in the drainage and production stage,achieving a great breakthrough in the shale oil exploration for Member 2 of Funing Formation in Gaoyou sag.Based on the observations of cores and thin sections from wells such as Well HY1,whole rock mineral composition analysis by X-ray diffraction,nitrogen adsorption analysis,nuclear magnetic resonance analysis,and organic geochemical analysis of frozen cores,in combination with the dynamic production data of Well HY1HF and Well H2CHF,the paper systematically analyzes the geological characteristics of Member 2 of Funing Formation in Gaoyou sag,and further reveals the enrichment regularities and controlling factors of shale oil from Member 2 of Funing Formation in Subei Basin.Semi-deep to deep lacustrine subfacies shale are developed in Member 2 of Funing Formation of Gaoyou sag,characterized by large thickness and wide distribution,laying the foundation for the enrichment of shale oil.Shale lithofacies control the horizontal and longitudinal distribution of"source sweet spots"and"reservoir sweet spots",among which the lithofacies with relatively high content of clay minerals correspond to good hydrocarbon generation potential,and those with high content of felsic minerals and carbonate minerals have good physical properties and pore-throat structure.According to the characteristics of lithologic association,the shale oil reservoir in Member 2 of Funing Formation can be divided into three types,i.e.,self-generating and self-preserving shale oil(TypeⅠ),mud generating and carbonate preserving shale oil(TypeⅡ),and mud generating and silty laminae preserving shale oil(TypeⅢ).High-quality pore-fracture system is developed in the source-reservoir combination of TypeⅡshale oil,characterized by good oil content and high mobility.Moreover,the existing dynamic production data indicate that TypeⅡshale oil reservoir has good productivity.In addition,good preservation conditions and pressurization resulted from secondary hydrocarbon generation are the key to high and stable production of shale oil.The shale oil exploration breakthrough in Member 2 of Funing Formation of Gaoyou sag indicates that the Paleogene shale oil in Subei Basin has good exploration prospects and Gaoyou sag is a key area for increasing reserves and production.These research results have important reference and guiding significance for the exploration and exploitation of shale oil in continental faulted basins in eastern China.