关键词: 陆相页岩油, 页岩储层, 孔隙类型, 无机孔, 渤南洼陷, 高邮凹陷, 复兴地区

Abstract: Significant progress has been made in the exploration and development of continental shale oil in China, which has become a major field for increasing oil reserves and production. In order to investigate continental shale lithofacies and reservoir pore development characteristics and their influencing factors, two main types of shale have been studied and compared, including the mixed shale in the Lower sub-member of the third member of Shahejie Formation (Lower Sha 3 sub-member) in Bonan subsag in Jiyang Depression and the second member of Funing Formation (Fu 2 member) in Gaoyou Sag in Subei Basin, as well as the matrix shale in Dongyuemiao member and the second member of Lianggaoshan Formation (Liang 2 member) in Fuxing area in Sichuan Basin. Based on core observation and description, multiple experimental and testing techniques such as bulk rock mineral X-ray diffraction, thin section, micro area XRF, high-pressure mercury injection–low-temperature nitrogen adsorption joint measurement, micro CT, argon ion polishing scanning electron microscopy, and overburden porosity have been used to comprehensively characterize and analyze the lithofacies and reservoir pores of continental shale, and identify influencing factors for reservoir pore development. The study results indicate that multi-component and multi-scale sedimentary structures were developed in continental shale. Controlled by the alternating input of terrestrial and endogenous materials, the sedimentary structure combination types and lithofacies types of mixed shale are more abundant and diverse than the matrix shale. In Bonan subsag, the lithofacies is mainly composed of layered carbonate mixed shale, layered felsic mixed shale, laminated carbonate shale, and massive carbonate shale. In Gaoyou Sag, it is mainly composed of laminated felsic mixed shale, laminated carbonate shale, layered felsic shale, and massive clayey mixed shale. In Fuxing area, it is mainly composed of massive clayey shale, laminated shell carbonate shale, or laminated felsic shale. Based on the differences in pore carriers, the pore classification scheme for continental shale oil reservoirs has been established, proposing that pores can be formed in various inorganic minerals and organic matter components in continental shale, with the most favorable pore carriers of carbonate minerals and clay minerals. In Bonan subsag, pores are dominated by carbonate mineral pores. In Gaoyou Sag, they are mainly carbonate mineral pores and felsic mineral pores. In Fuxing area, pores are mainly clay mineral pores and carbonate mineral pores. The high-quality lithofacies was the foundation for pore development, and differences in mineral composition, structure, and sedimentary structures all affected the degree of pore development. The pores were well developed in massive clayey (mixed) shale and laminated carbonate (mixed) shale, fairly developed in laminated (layered) felsic (mixed) shale, but poorly developed in massive carbonate (mixed) shale; The diagenetic type and evolutionary sequence were key factors controlling the formation and preservation of reservoir pores. The rigid mineral particles were stacked in layers or locally mixed to form anti compaction support structures, which were beneficial for pore preservation, while the common pore increasing process included clay mineral transformation and carbonate mineral dissolution. In Bonan subsag and Gaoyou Sag, inorganic pores in mixed shale were mainly controlled by compaction, recrystallization, and dissolution, but there were basically no organic matter pores; In Fuxing area, the inorganic pores of matrix shale were controlled by compaction, clay mineral transformation, and shell calcite dissolution, and organic matter pores were developed in bitumenite.

Key words: continental shale oil, shale reservoir, pore type, inorganic pore, Bonan subsag, Gaoyou Sag, Fuxing area