The Permian tight clastic reservoir and Ordovician carbonate reservoir were developed in the central-southern Ordos Basin. This study investigated the fluid inclusion petrography, diagenetic fluid characteristics, formation process of natural gas reservoir, source rock characteristics, and reservoir accumulation characteristics of these Paleozoic strata by petrographic observations, scanning electron microscope imaging, fluid inclusion homogenization temperature, salinity, laser Raman spectrum, and gas chromatograph analyses. The results have suggested two phases of fluid inclusions in both the Permian sandstone and the Ordovician Majiagou Formation dolomite reservoirs, and the fluid inclusions recorded the history from the early thermal evolution of hydrocarbon generation to the formation, migration, and accumulation of natural gas. The early-phase inclusions show weak yellow fluorescence and recorded the early formation of liquid hydrocarbons, while the late-phase inclusions are nonfluorescent natural gas inclusions distributed in the late tectonic fractures and recorded the late accumulation of natural gas. The brine systems of the Permian and Ordovician fluid inclusions are, respectively, dominated by CaCl₂-H₂O and MgCl₂-NaCl-H₂O. The diagenetic fluids were in the ranges of medium-low temperature and moderate-low salinity. The natural gas hydrocarbon source rocks in the Ordos Basin include both the Permian coal-bearing rocks and the Ordovician carbonates. The process of the early-phase liquid hydrocarbon formation and migration into the reservoir corresponded to 220 Ma (Late Triassic). The late large-scale migration and accumulation of natural gas occurred at 100 Ma (early Late Cretaceous), which was close to the inclusion Rb/Sr isochron age of 89.18 Ma, indicating that the natural gas accumulation was related to the Yanshanian tectonic movement.

中文翻译：

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有机包裹体记录的鄂尔多斯盆地中南部古生界储层成藏特征

鄂尔多斯盆地中南部发育二叠系致密碎屑岩油藏和奥陶系碳酸盐岩油藏。本研究通过岩相学观测、扫描电镜成像、流​​体包裹体均质化温度、盐度、激光拉曼光谱等研究了这些古生界地层的流体包裹体岩相学、成岩流体特征、天然气成藏过程、烃源岩特征和储层成藏特征。和气相色谱分析。结果表明，二叠系砂岩和奥陶系马家沟组白云岩储集层均存在两期流体包裹体，流体包裹体记录了从早期生烃热演化到天然气形成、运移和聚集的历史。早期包裹体呈弱黄色荧光，记录了液态烃的早期形成，而晚期包裹体是分布在晚期构造裂缝中的无荧光天然气包裹体，记录了天然气的晚期聚集。二叠系和奥陶系流体包裹体的卤水体系分别以氯化钙为主₂ -H ₂ O和MgCl ₂ -NaCl-H ₂ O。成岩流体处于中低温和中低盐度范围内。鄂尔多斯盆地天然气烃源岩包括二叠系含煤岩和奥陶系碳酸盐岩。早期液态烃形成和运移进入储层的过程对应于220 Ma（晚三叠世）。天然气大规模运移聚集发生在100 Ma（晚白垩世早期），接近包裹体Rb/Sr等时线年龄89.18 Ma，表明天然气成藏与燕山期构造运动有关。