## 1 Introduction  
The Ordos Basin is one of China's most important energy basins, with a total proven petroleum reserve of 8.6 billion tons. Within the basin, the Yan'an Formation plays a critical role plays a critical role as a major reservoir for hydrocarbons [1; 2; 3]. Recent breakthroughs in unconventional oil and gas exploration technologies have significantly heightened interest in the exploration and study of the Ordos Basin [4; 5].  
Previous studies of the Ordos Basin have predominantly focused on tectonic evolution [6; 7; 8; 9], sedimentological characteristics [6; 10; 11; 12; 13; 14], fault systems [15; 16; 17; 18; 19], formation pressure [20; 21; 22], and geothermal variations [23; 24]. The tectonic evolution of the Ordos Basin can be divided into eight stages: (1) Development of the crystalline basement from the Archean to Early Proterozoic; (2) Continental rifting during the early to middle Mesoproterozoic, leading to the formation of marginal rift valleys and intracontinental downwarp troughs; (3) Continental convergence from the Late Mesoproterozoic to Early Neoproterozoic, causing uplift and sediment starvation in the basin; (4) Marginal rifting and intracontinental depression from the Mid-Neoproterozoic to the Middle Ordovician of the Early Paleozoic, leading to the deposition of marine carbonate platforms; (5) Peripheral orogenic collisions from the Late Ordovician to Early Carboniferous of the Early Paleozoic, resulting in basin uplift and significant erosion; (6) Peripheral rifting from the Late Carboniferous to the end of the Permian in the Late Paleozoic, giving rise to marine-terrestrial transitional deposits; (7) Intracontinental depression in the Mesozoic, with the uplift along the basin margins and overall tilting, forming fluvial, deltaic, and lacustrine environments; (8) Peripheral fault activity during the Cenozoic, marking the final stage of tectonic development in the basin [6; 7; 8; 9]. Studies on the sedimentary features of the Ordos Basin mainly focus on the Late Triassic to Early Cretaceous, which is characterized by being rich in resources like oil, gas, coal, and uranium. The predominant sedimentary environments during this period include fluvial, deltaic, and lacustrine deposits [6; 10; 11; 12; 13; 14]. The basin's periphery is marked by numerous compression-related faults. The western edge features a thrust fault zone trending north-south, while the eastern edge is characterized by reverse faults dipping westward and associated folds. The northern part of the basin exhibits large-scale rift-associated reverse structures, and the southwestern area has several negative flower structures [15; 16; 17; 18; 19]. Formation pressure is critical in driving fluid migration in the basin and is crucial for locating fluid-related mineral resources. The Ordos Basin experienced overpressure during the Early Cretaceous, but currently, the strata exhibit abnormally low pressures [20; 21; 22]. The geothermal gradient in the basin averages 2.93 \({}^{\circ}\)C per 100 m, with an average heat flow value of 61.78 mW/m\({}^{2}\)[23; 24].  
The interaction between tectonic movements, sedimentary environments, and source rock composition is crucial for determining sedimentary facies characteristics, yet relatively little attention has been paid to this aspect [23; 24; 25; 26; 27; 28]. Understanding the tectonic and sedimentary features of the Yan'an Formation is particularly important for studying hydrocarbon reservoirs. This paper collects extensive well logging data, lithology data, and tectonic information on the Yan'an Formation, integrating field profiles with previous research to analyze the sequence stratigraphy, tectonic sedimentology, and reservoir characteristics of the Yan'an Formation in the Ordos Basin. The analysis identifies the intrinsic factors that make the Yan'an Formation a high-quality hydrocarbon reservoir and offers technical guidance for oil and gas exploration and development.