关键词: 鄂尔多斯盆地, 陆相页岩油, 延长组7段, 富集条件, 资源潜力

Abstract: PetroChina Changqing Oilfield Company has discovered Qingcheng oilfield in the source rock stratum of Member 7 of Triassic Yanchang Formation in Ordos Basin; it is a billion-ton-level shale oilfield with the proven geological reserves totalling 11.53×10⁸ t, and has built China’s first development demonstration zone of megaton monoblock shale oil in Longdpng area. This paper systematically reviews the exploration and development history of shale oil of Member 7 of Yanchang Formation in Ordos Basin, summarizes the enrichment conditions of shale oil and sweet-spot optimization, and analyzes the resource prospects for shale oil exploration and development. During the deposition period of Member 7 of Yanchang Formation, Ordos Basin was a large, wide and gentle inland depression lake basin, where the lake basin environment with high productivity and strong reductivity was conductive to the deposition of organic matter-rich shale, the development of multi-stage slope break belt and frequent seismic and volcanic activities were conductive to the development of various deep-water gravity flow deposits, and the large-area contact between fine-grained sandstone and shale basin as well as the strong hydrocarbon generation and expulsion of the organic matter-rich source rocks of shale oil co-existing with reservoirs provided an impetus for the intra-source migration and enrichment of shale oil of Member 7 of Yanchang Formation; the micro-nano-scale pore throat-fracture network coupling system composed of intergranular pores, dissolved pores, clay mineral intercrystalline pores and micro-fractures is the main enrichment unit of shale oil, which controls the final enrichment of shale oil. In the migration process of hydrocarbons from shale to sandstone interlayer, the chromatographic action of shale urges the sandstone interlayer to be enriched with high-quality hydrocarbons, which have the characteristics of light oil, low viscosity and good fluidity, thus forming the key sweet spots for the efficient development of low-pressure shale oil of Member 7 of Yanchang Formation. In addition, the migrating shale oil that can be beneficially developed in the central lake basin is the realistic target of increasing the reserve and production of shale oil, while the migrating oil that can be beneficially developed at the edge of the lake basin is the stand-by exploration field for stabilizing and increasing the production of shale oil of Member 7 of Yanchang Formation. Focusing on Qingcheng oilfield and its periphery, to expand the exploration achievements of migrating shale oil and actively explore the development potential of retained shale oil are important measures to accelerate the secondary development of Changqing oilfield and guarantee national energy security.

Key words: Ordos Basin, continental shale oil, Member 7 of Yanchang Formation, enrichment condition, resource potential