## 1 Introduction  
As the international geopolitical situation becomes more complex and severe, the international oil and gas market pattern and the factors affecting supply security have undergone profound changes, and the uncertainty of the external environment has increased. China's dependence on foreign countries for oil and gas remains high, and oil and gas supply security is facing new problems and challenges [1,2]. As one of the largest oil- and gas-bearing basins in China, the exploration and development of oil and gas resources in the Tarim Basin is of great significance to ensuring national energy security. In recent years, as the discovery rate of structural traps in the Tarim Basin decreases year by year, the exploration focus is shifting to lithologic oil and gas reservoirs, and the efficient development of such reservoirs has become the key path to break through the bottleneck of reservoir increase [3-6]. Thin-layer sand bodies, as one of the important reservoir types in lithological oil and gas reservoirs, are widely distributed in sedimentary environments such as lake deltas, delta fronts, shallow sea shelves, and river facies worldwide [7-10]. They have the characteristics of small thickness, fast lateral variation, and strong heterogeneity. Identification of their sedimentary characteristics and reservoir prediction have always been difficult points in oil and gas exploration [11-14]. Tahe Oilfield is located in the northern margin of Tarim Basin, where typical thin sand bodies are developed in the formation of the fourth member of the Triassic system. The discovery of several high-yield wells has confirmed its huge exploration potential [15].  
The sand body of the fourth section of Tahe Oilfield is characterized by a typical \"mud-wrapped sand\" structure and strong heterogeneity. In previous studies, scholars have mainly focused on the study of the long strip-shaped sand bodies distributed nearly parallel to the fourth section, lacking research on the integrity of the sand body of the fourth section of Tahe Oilfield. Moreover, there is still controversy over the formation mechanism of the long strip-shaped sand bodies, such as \"river sand\" and \"lake shore sand bars\". At present, there is still insufficient research on the sand bodies in the fourth member of the study area, and the unclear sedimentary facies characteristics and sand body distribution pose challenges for further development of the oilfield. Therefore, it is necessary to conduct systematic research on the sand bodies in the study area again.  
In this paper, the sedimentary facies types and sand body distribution characteristics of the fourth member of the Triassic System in Tahe Area are analyzed by comprehensively using core, logging, and seismic data. Research indicates that the strata in the fourth member of the Triassic in the Tahe Oilfield are primarily indicative of marginal lacustrine subfacies deposition, with delta-front subfacies developing in certain local areas. This study provides a scientific basis for the direction of oil and gas exploration in Tahe Area by clarifying the development law of sedimentary facies and sand bodies, and further analyzing the significance of oil and gas accumulation.