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

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