## 6 Conclusions  
Based on a comprehensive vertical stratigraphic analysis integrating lithofacies types and bedding characteristics, the Shaximiao Formation in the study area can be classified into three distinct lithofacies assemblages: Type I (high-porosity and high-permeability lithofacies) has Type I (1) sandstone lithofacies and medium-scale cross-bedded medium-grained sandstone, indicating well-developed reservoir physical properties and high porosity. Type II (medium-porosity and medium-permeability lithofacies) is characterized by a combination of Type II (1) sandstone lithofacies, Type II (2) sandstone lithofacies, and Type II (3) sandstone lithofacies that reflect moderate reservoir quality with variable sediment sorting and permeability. Type III (low-porosity and low-permeability lithofacies) consists of Type III (1) sandstone lithofacies and Type III (2) sandstone lithofacies that suggest limited reservoir potential due to finer grain size, poorer sorting, and reduced porosity.  
Six distinct sandbody types were identified in the study area: deeply incised abrupt-transition sandbody (A), deeply incised gradual-transition sandbody (B), growth gradual-transition sandbody (C), progradational superimposed sandbody (D), progradational mouth bar (E), and suspension accretion sandbody (F). The sandbodies (A) and (B) are primarily found in the distributary channel microfacies of the delta plain subfacies. Sand  
Figure 9: Porosity of sandbodies with different genetic types. Note: The porosity values represent logging porosity.  
body (C) is located in the distributary channel microfacies within the transitional zone between the delta plain and delta front subfacies. By contrast, sandbodies (D), (E), and (F) develop in the subaqueous distributary channel and distal mouth bar microfacies of the delta front subfacies. This study confirmed that high-quality reservoirs mainly develop within deeply incised abrupt-transition and gradual-transition channels, where depositional processes exert significant control over reservoir properties. Specifically, the deeply incised abrupt-transition sandbody (A), deeply incised gradual-transition sandbody (B), and growth gradual-transition sandbody (C) demonstrate average porosity and thickness, making them the most favorable for reservoir development. In comparison, the progradational superimposed sandbody (D), progradational mouth bar (E), and suspension accretion sandbody (F) exhibit relatively lower porosity and reduced thickness, indicating their comparatively lesser potential for reservoir quality.  
All the authors actively contributed to the preparation of this research article. Data curation, methodology, and funding acquisition, H.L.; writing--original draft and writing--review and editing, T.L. ([PERSON]); funding acquisition, investigation, project administration, and resources, L.J., T.L. ([PERSON]), C.G. and C.L.; supervision and visualization, H.D.; formal analysis, software, and validation, Y.Y. and D.W.; writing--review and editing, M.F. All authors have read and agreed to the published version of the manuscript.  
This research was funded by the Shunan Gas Mine, PetroChina Southwest Oil & Gasfield Company, grant number 2023 ZX03-02. And The APC was funded by the Shunan Gas Mine, PetroChina Southwest Oil & Gasfield Company.  
Not applicable.  
All relevant data and materials are presented in this published article.  
Our sincere thanks go out to the PetroChina core repository staff for their strong support in sample collection. We also greatly appreciate the editor and anonymous reviewers for their valuable and constructive comments, whose professional suggestions helped improve our manuscript.  
Authors [PERSON], [PERSON], [PERSON], [PERSON] and [PERSON] were employed by the company PetroChina Southwest Oil & Gasfield Company. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.