Abstract: Jiyang depression boasts large shale oil resources, with peak oil production exceeding 100 t/d in multiple subsags and horizontal wells, making a good beginning for the shale oil revolution. The shale in Jiyang depression is characterized by saline and carbonate-rich components, with widely developed laminated structure. Laminated structure can provide an important basis for lithofacies classification, and basic information for reservoir characteristic analysis. The variations in laminated structure are important factors that cause differences in shale pore structures and thus affect reservoir quality. Through detailed description of cores, whole rock X-ray diffraction analysis, thin section identification, field emission scanning electron microscopy analysis, and nuclear magnetic resonance experiments, the development types and characteristics of carbonate-rich shale laminae in Jiyang depression have been clarified as below. (1)Lamina features control the type and pore size distribution of shale pores. The medium to large pores are mainly developed in calcareous lamina which are the main carriers of connected pores and effective reservoir units in shale. With the increase of calcite recrystallization, intergranular fractures are more developed and pore connectivity is better. The argillaceous laminae are dominated by medium to small pores with poor connectivity, but rich in organic matters, playing a role as the main oil generating unit. (2)Bedding fracture, as an important matrix micro-fracture type of shale in Jiyang depression, are commonly developed in the continuous sparry calcareous laminated shale with high organic matters and the continuous cryptocrystalline calcareous laminated shale with low sedimentation rate, high evolution degree and frequency interbedding. (3)The thin interbedded calcareous-argillaceous pair structure is a high-quality laminated structure of carbonate-rich shale in Jiyang depression. The better the lamina density and lateral continuity, the more developed the multi-scale and multi-type pore network, and the better the reservoir quality. The laminated structure plays a role as the "high-speed channel" in controlling reservoir quality. The organic-rich continuous laminated shale is the optimal development target for shale oil in Jiyang depression, which provides the geological theoretical basis for optimization of sweet spots and golden development targets of shale oil at present.

Key words: Jiyang depression, shale lamina, connectivity, pore-fracture pattern, bedding fracture, reservoir quality

摘要： 济阳坳陷页岩油资源量大,多洼陷、多口水平井的峰值产油量超过100 t/d,初步实现了页岩油革命的良好开端。济阳坳陷页岩具有咸化富碳酸盐组分的特征,且页岩层系中广泛发育特色的纹层结构。纹层结构是页岩岩相划分的重要依据,可为页岩储集特征的分析提供基础信息。页岩纹层结构的差异是造成页岩孔隙结构差异,进而影响储层品质的重要因素。通过开展岩心精细描述、全岩X射线衍射分析、岩石薄片鉴定、场发射扫描电镜分析、核磁共振实验等,明确了济阳坳陷富碳酸盐页岩纹层的发育类型及特征。①纹层特征控制页岩的孔隙类型和孔径分布。灰质纹层发育中孔—大孔,是页岩连通孔隙的主要载体,也是页岩主要的有效储集单元,且随着方解石重结晶程度增加,晶间缝更发育,孔隙连通性越好;泥质纹层以发育中孔—小孔为主,孔隙连通性差,但富集有机质,是主要的生油单元。②层理缝是济阳坳陷页岩重要的基质微缝类型,在高有机质连续亮晶灰质纹层页岩和低沉积速率、较高演化程度、高频互层的连续隐晶灰质纹层页岩中普遍发育。③薄互层的灰质-泥质"层偶"结构是济阳坳陷富碳酸盐页岩的优质纹层结构,纹层的密度和横向连续性越好,多尺度、多类型孔缝网络越发育,储层品质越好。纹层结构在储层中起到了"高速通道"的作用。富有机质连续纹层页岩是济阳坳陷页岩油的优选开发对象,这一研究认识为现阶段页岩油"甜点"和黄金靶体开发目标的优选提供了地质理论基础。

关键词: 济阳坳陷, 页岩纹层, 连通性, 孔缝模式, 层理缝, 储层品质