## 1 Introduction  
The concept of shallow-water deltas was first proposed by [PERSON] during his study of the Mississippi River Delta [1], and was further enriched by [PERSON] in his research on the Carboniferous terrestrial seas in the United States [2]. The sedimentary evolution and main controlling factors of Nenjiang Formation in North Da 'an area of the southern Songliao Basin are discussed, and two sedimentary models of shallow-water deltas are established [3]. [PERSON] et al. 's study is predominantly intended to explore the distribution rule of the sand body of the Zhuhai Formation on the north slope of the BaiyunSag [4]. Channel dimensions are generally smaller in the medial areas, but sizes are variable: deposits are of braided, meandering, and simple channels which show varying degrees of lateral migration [5]. Sedimentological facies models for (semi-)isolated basins are less well developed than those for marine environments, but are critical for our understanding of both present-day and ancient deltaic sediment records in restricted depositional environments [6]. Currently, shallow-water delta sediments have been found in the Mesozoic and Cenozoic strata of basins such as Bohai Bay, Ordos, and Songliao in China [7]. These deposits have formed large-scale oil and gas reservoirs, showcasing significant exploration potential [8]. The delta-front sand bodies of shallow-water deltas are diverse in type, possess good reservoir properties, and offer favorable conditions for oil and gas accumulation, making them important reservoir facies for hydrocarbons. Therefore, conducting in-depth research on the delta-front architecture models of shallow-water deltas is crucial for future oil and gas exploration and development. The Ordos Basin, a crucial Chinese oil and gas source, features low-permeability lithological reservoirs. These reservoirs have tight rock formations with minimal pore space, restricting fluid flow. During the Triassic period, the Chang 8 oil reservoir group of the Upper Triassic Yanchang Formation in the Ordos Basin experienced continuous subsidence and stable settling, forming shallow-water river-lake facies deposits with a river-lake source clastic rock sequence [9; 10; 11]. Among them, the Chang 8 oil reservoir group developed typical shallow-water delta deposits. Previous studies on the shallow-water delta depositional facies of the Yanchang Formation in the Ordos Basin have been extensive. [PERSON] et al. [12], guided by high-resolution sequence stratigraphy analysis, conducted detailed stratigraphic correlations and small-scale sand body divisions for the Chang 8 oil group in the Jiyuan area. Based on this, they created a top structure map and a planar distribution map of the small sand bodies under isochronous conditions, which refer to the geological principle that all points on a given stratigraphic surface are of the same age. [PERSON] et al. [13], through extensive core observations, concluded that the Chang 8 oil reservoir group in the northwest part of the Ordos Basin predominantly developed shallow-water delta-front subfacies deposits. Subaqueous distributary channels were the main depositional microfacies, with large, far-reaching sand bodies characterized by local thick sand bodies in the river channel direction forming mound-like distributions, and mound-like sand bodies surrounding the lake basin in a ring-shaped pattern in the vertical river channel direction. Although there has been considerable research on the depositional microfacies and sedimentary characteristics of shallow-water deltas in the Ordos Basin, especially the Chang 8 oil reservoir group of the Yanchang Formation, studies on the characterization of individual sand bodies, especially in the context of their sedimentary background, remain relatively limited. This article takes the Chang 8 oil reservoir group in the Luo 1 well area of the Jiyuan Oilfield as an example, utilizing core, logging, and production dynamic data to characterize individual sand bodies.