###### Abstract  
The sedimentary characteristics and model of the shallow-water delta front are of great significance for the development of oil and gas reservoirs. At present, there are great differences in the understanding of the distribution patterns of estuary dams in the shallow-water delta front. Therefore, this paper reveals the distribution characteristics of estuary dams through the detailed dissection of the Qing 1 Member in the Daqingzijing area and establishes a completely new distribution pattern of estuary dams. By using geological data such as logging and core measurements, sedimentary microfacies at the shallow-water delta front are classified and logging facies identification charts for each sedimentary microfacies are developed. Based on the analysis of single-well and profile facies, the sedimentary evolution laws of the Qing 1 Member reservoirs are analyzed. On this basis, the sedimentary characteristics and model of the lacustrine shallow-water delta front are established. The results indicate that the Qing 1 Member in the Daqingzijing area exhibits a transitional sequence from a delta front to pro-delta facies and finally to deep lacustrine facies, with sediments continuously retrograding upward. Subaqueous distributary channels and estuary dams constitute the skeletal sand bodies of the retrogradational shallow-water delta. The estuary dam sand bodies are distributed on both sides of the subaqueous distributary channels, with sand body development gradually decreasing in scale from bottom to top. These bodies are intermittently distributed, overlapping, and laterally connected in plan view, challenging the conventional understanding that estuary dams only occur at the bifurcation points of underwater distributary channels. Establishing the sedimentary characteristics and model of the shallow-water delta front is of great significance for the exploration and development of reservoirs with similar sedimentary settings. delta front; sedimentary characteristics; evolution model; Qing 1 Member 2025 23 July 20  
examined sedimentary characteristics and formation dynamics, and they have pointed out that the Gilbert three-layer structure is not developed in shallow deltas [6; 7; 8; 9; 10; 11; 12; 13]. Exploration and development practices have demonstrated that shallow-water deltas host abundant oil and gas resources. In recent years, such deltas have become key targets for lithologic hydrocarbon reservoir exploration. The sedimentary characteristics and spatial distribution of sand bodies form the geological foundation for reservoir development planning and are critical factors influencing the success rate of hydrocarbon exploration and production. The Daqingzijing area is located in the southern part of the Songliao Basin. Recent research shows that depression basins, due to their overall tectonic stability and gentle terrain, are sites for the development of large shallow-water deltas. The traditional view holds that the Songliao Basin follows the lake-controlled shallow-water delta sedimentary model. It has been summarized as a lobate model, characterized by thin individual delta bodies with widespread distribution, numerous distributary channels, extensive frontal sheet sands, and well-developed facies differentiation. Previous studies have generally concluded that estuary dam sands are poorly developed and are primarily located at the bifurcation points of underwater distributary channels [14; 15], and they belong to the underwater distributary channel-type shallow-water delta front. However, with the encryption of the development well network and increased understanding of depositional factors, it is found that the delta front is not a simple depositional feature dominated by underwater distributary channels. Core observation and well logging curve analysis both indicate that there are extensive estuary dams, both of which are developed at the same time. This undoubtedly overturns the traditional geological understanding and urgently requires the exploration of a new sedimentary model.