## 6 Conclusions  
Differentiated interval structural characteristics of the Wufeng-Longmaxi Formation deep shale reservoirs in the western Chongqing area were studied through an experimental investigation based on low-field nuclear magnetic resonance (NMR) and fractal modeling methods. The following conclusions were obtained in this study.  
1. The pore structure of the Wufeng-Longmaxi Formation shale from the western Chongqing area was fractal to a degree. The fractal dimension of bound fluid pores (D\({}_{1}\)) based on NMR tests ranged from 1.6895 to 2.3821, and the fractal dimension of movable fluid pores (D\({}_{2}\)) ranged from 2.9914 to 2.9996, indicating that the pore systems are complicated and heterogeneous. In addition, both D\({}_{1}\) and D\({}_{2}\) can represent the complexity of the overall pore structure in the middle and upper Longmaxi Formation.
2. The pore size distribution in the Wufeng-Longmaxi shale samples in the Z-3 well was mainly in the range of 1-100 nm and 100 nm-1 \(\upmu\)m, concentrated between 1 nm and 100 nm. Mesopores and micropores provided a large proportion of the pore volume, and micropores comprised the major microstorage space.
3. The exponential correlation between shale permeability and porosity was strong. D\({}_{1}\) and D\({}_{2}\) had no apparent correlation with permeability and porosity, while fractal dimensions had moderately positive correlations with TOC content in the lower S\({}_{1}\)[1]-[1] sub-layer and its upper layers.  
Figure 15: The relationship between gas content and TOC, quartz content of shale samples in the Z-3 well.  
* (4) TOC content was one of the major factors influencing the gas content in the Wufeng-Longmaxi Formation shale in the Z-3 well. Specifically, an increase in TOC content resulted in greater porosity, leading to a more abundant organic matter pore network and enhanced homogeneity of the pore structure in the bottom S\({}_{1}\)[11-1 sub-layer, which showed significant potential for the exploration of shale gas.  
Conceptualization, D.Z., X.Z. and G.W.; Methodology, D.Z., Q.W., X.Z. and G.W.; Software, D.L., Y.W., Q.W. and X.Z.; Validation, D.L.; Formal analysis, D.Z. and D.L.; Investigation, D.Z., D.L., Y.W. and S.W.; Resources, D.Z., S.W., W.J. and Y.G.; Data curation, Y.W. and W.J.; Writing--original draft, D.L.; Writing--review & editing, D.Z., Y.G. and G.W.; Visualization, D.L. and Y.G.; Supervision, D.Z. and G.W.; Project administration, D.Z.; Funding acquisition, D.Z. All authors have read and agreed to the published version of the manuscript.  
This work was founded by the Natural Science Foundation of Jiangsu Province (No. BK20210521), Provincial College Student Innovation Training Project of Jiangsu Province (No. 202310290234Y/202310290500H/202310290501H), the Natural Science Foundation of China (No. 41772130/52374105/52204113), the Fundamental Research Funds for the Central Universities (No. 2021 QN1061), the Natural Science Foundation of Chongqing City (No. cstc2021 jcyj-msxmX0624), the \"Energy and Environment Youth Talent Training Program\" by the China Energy Society, China Environmental Protection Foundation, and Beijing Energy Society (No. RCH2022081), and the Science and Technology Research Project of the Chongqing Education Commission (No. KJZD-K202103201).  
Not applicable.  
The dataset is available on request from the authors.  
Thanks to the reviewers for their suggestions. Thanks to [PERSON] from China University of Mining & Technology for his suggestions on the research process.  
The authors declare no conflict of interest.