渤海湾盆地南堡凹陷沙河街组一段泥页岩微观孔隙特征及其主控因素

Micro⁃pore characteristics and its main controlling factors of shale in Sha 1 Member of Shahejie Formation in Nanpu Sag of Bohai Bay Basin

为阐明渤海湾盆地南堡凹陷沙河街组一段湖相页岩的微观孔隙结构,深化泥页岩储集性能认识,通过氩离子抛光扫描电镜、恒速压汞及低温氮气吸附实验等方法,对沙一段泥页岩微观孔隙结构进行深入研究。结果表明:沙一段泥页岩储层储集空间以粒间孔、晶间孔、粒内孔、溶蚀孔及微裂缝为主,部分储集空间被有机质充填,发育少量有机质溶孔;储层微米级孔隙以大孔隙(孔隙半径≥100μm)和微小孔隙(孔隙半径<50μm)为主,纳米级微孔隙以微孔(孔隙半径<10 nm)为主;喉道以粗喉道、细喉道和微细喉道为主,非均质性较强;受地层异常高压及脆性矿物含量的影响,泥页岩储层岩石脆性较强,裂缝较发育,物性较好,有利于后期的页岩油气开采;由于泥页岩有机质成熟度较低,部分烃类物质滞留于储层中,堵塞了部分孔隙,降低了孔喉连通性。研究成果可为南堡凹陷页岩油有利区的优选提供理论依据。

In order to clarify micro-pore structure of lacustrine shale in Sha 1 Member of Shahejie Formation in Nan⁃pu Sag of Bohai Bay Basin,and to deepen the understanding of shale reservoir performance,micro-pore structure of shale in Sha 1 Member is finely characterized by means of argon-ion polishing SEM,constant-rate mercury intru⁃sion and low-temperature nitrogen adsorption experiments.The results show that reservoir space of shale reservoir in Sha 1 Member of Shahejie Formation is mainly composed of intergranular pores,intercrystalline pores,intragranu⁃lar pores,dissolution pores and microfractures.Some reservoir spaces are filled with organic matter,developing small amount of organic matter dissolved pores.Micron-scale pores in reservoir are mainly macropores(pore radius≥100μm)and micropores(pore radius<50μm).Nano-scale micropores are dominated by micropores(pore radius<10 nm).Pore throats are mainly coarse throats,fine throats and micro-fine throats with high heterogeneity.Affected by abnormal high formation pressure and brittle minerals content,shale reservoir rock has high brittleness and well developed fractures,with good physical properties,being conducive to later shale oil and gas production.Low organ⁃ic matter maturity causes part of hydrocarbon substances retained in the reservoir,blocking some pores and reduc⁃ing pore throat connectivity.The research provides theoretical basis for the optimization of shale oil favorable areas in Nanpu Sag.