## 4 Result and Discussion  
### Sedimentary Petrological Characteristics  
The rock types present in the target layer, the S3 sand group in the Upper Karamay Formation, are diverse and exhibit coarse-grained sediments. Specifically, conglomerate and sandstone are the dominant rock types, accounting for 59.4% and 34% of the total composition, respectively. On closer examination, the lithology is primarily characterized by glutenite, small conglomerate, and gravel-bearing coarse sandstone, followed by medium-fine sandstone and siltstone. The clastic particles within the reservoir mainly comprise lithic and quartz, with lithic content accounting for nearly 80%. Tuff, metamorphic mudstone, and mudstone, resulting from rapid accumulation in the margin, are the main lithic components. Additionally, quartz content is 14.0% and feldspar content is 6.9%; the matrix primarily consists of argillaceous materials. Overall the composition maturity of the reservoir is considered to be low (Figure 5). The glutenite exhibits poor sorting and a subangular-subrounded shape (Figure 5h). The small conglomerate shows moderate sorting and is subrounded (Figure 5l). The main diagenesis is calcium cementation, with a dense to medium degree of cementation. Most particles are in linear contact, while some are compacted and embedded with each other. The rock sorting is generally poor, although some areas display medium sorting. Overall, the rock exhibits low structural maturity.  
The development of purple-red multiconglomerate mixed glutenite in the study area primarily indicates a typical onshore exposure environment (Figure 5b). This glutenite is characterized by a high matrix content, which is the product of event deposition during floods. Alternatively, the gray-brown and gray-green glutenites, as well as the sandy small conglomerate, exhibit better sorting and lower matrix content, and are primarily supported by particles. These characteristics reflect a stable traction flow during normal water periods. Although the small conglomerate lithology in this area is a favorable reservoir for oil (Figure 5c,e), it is present in relatively small proportions. The mudstone exhibits a diverse range of colors, including gray and gray-green, indicating a reducing sedimentary environment; variegated colors, indicating alternating water-land sedimentation; and brown, purple, and reddish-brown, indicating a sedimentary environment under oxidizing conditions. However, dark mudstone is absent, which is consistent with the shallow-water sedimentary environment in the study area. Furthermore, the presence of carbonaceous mudstone and coal line in the core well 1601 reflects the development of swamps in the delta plain. In general, the physical properties of the rock facies of the S3 sand group are mainly controlled by factors such as sorting and shale content differences caused by sedimentation, and cementation also affects the physical properties of the rock facies, but it is not the main factor.  
The sedimentary structures observed in the study area exhibit a wide range of variations, which can be attributed to the intricate hydrodynamic conditions. In the sections characterized by coarser lithology, there is a prevalence of massive, trough cross, and tabular cross beddings. Particularly, coarse-grained deposits, such as conglomerates, tend to display thick layers of massive structures. These layers are frequently interspersed with scouring interfaces and mud gravels, indicating rapid accumulation and local intense hydrodynamic activity. Conversely, fine-grained sections, such as sandstone, predominantly exhibit parallel, ripple, and inclined beddings.