## 1 Introduction  
Alluvial fans are fan-shaped accumulations formed when rivers (or floods) lose lateral constraint after exiting mountain ranges, leading to a decrease in flow velocity and the deposition of a large amount of material [1, 2, 3]. These are high-energy environment deposits. Previous studies, based on climate classification, have identified two types of alluvial fans:humid and arid [4; 5; 6; 7]. According to sediment transport mechanisms, alluvial fans can be further categorized into three types: debris flow-dominated, meandering river-dominated, and braided river-dominated fans [8; 9]. Compared to other types of land-based clastic deposits [10; 11], alluvial fans exhibit more complex internal structures. [PERSON], in his study of the Triassic modern alluvial fan in Karamay, subdivided the internal structure into three subfacies: fan root, fan middle, and fan edge, in a downstream direction. The sedimentary mechanisms and characteristics of these three areas vary significantly [12; 13]. The fan root has both debris flow and traction flow sedimentary mechanisms, while the fan middle and fan edge are primarily dominated by traction flow [14; 15]. The reservoir architecture in different subfacies of the alluvial fan is highly complex. [PERSON] and others made a more detailed subdivision, dividing the fan root into three architectural elements: channel flow zone, sheet flow zone, and overbank flow zone. The fan middle was divided into a braided flow zone and an overbank flow zone, while the fan edge was divided into a runoff zone and an overbank flow zone [8; 16; 17]. With continuous research on the complex architecture of alluvial fans, scholars have recognized significant differences in the architecture of different types of alluvial fans. However, due to the influence of multiple factors on sedimentary mechanisms and processes, the reservoir quality characteristics of alluvial fans vary, leading to the concept of \"thousand fans, thousand faces\" [18]. Therefore, establishing a highly generalized model with universal applicability is challenging, and it is necessary to conduct specific studies on the target fan architecture in the study area, considering its actual geological background. While building on [PERSON]'s framework, our work advances three key innovations: (1) Quantitative scaling relationships for arid-climate alluvial fan fringes (Section 4.4), (2) Evidence of base-level control on lobe connectivity (Section 4.2), and (3) Operational criteria for boundary identification (Section 3.3). These contributions address the \"thousand fans\" paradox by providing measurable parameters for gentle-slope systems. The Kekeya oil and gas field represents one of the early discoveries in the Tarim Basin, featuring a structurally controlled stratified hydrocarbon reservoir with primary production from the Neogene Xihepu Formation and Paleogene Kalatar Formation [19; 20; 21]. However, the field's complex geological setting has posed significant challenges in identifying high-quality remaining hydrocarbon-rich zones within its main producing intervals. Initial reservoir characterization efforts treated the target formation as a single connected sand body system, constrained by limited understanding of sedimentary distribution patterns at the well-group scale. This simplified approach has become increasingly inconsistent with accumulated production data, while current challenges of low formation pressure further necessitate refined reservoir characterization for development optimization. The complex architecture of fluvial sand bodies in this setting results from multiple controlling factors, including sediment source variations, topographic influences, and climatic conditions. These sand bodies exhibit characteristic lateral channel migration and vertical stacking patterns that create significant heterogeneity in spatial distribution and connectivity.