## 5 Conclusions  
(1) Shales of the Dalong Formation in the Western Hubei trough are dominated by siliceous shale lithofacies, with an average quartz content of 62.2%. Bioclastic limestones and marks are developed at the bottom and top of the formation. The Dalong Formation shales contain much type-I organic matter (averaging 6.66 wt.% TOC) at a stage of over-maturity (\(R_{\rm o}\) = 2.56-2.79%). Organic matter content is positively correlated with clay mineral content and weakly negatively correlated with quartz and carbonate mineral contents. (2) The total porosity and permeability of the Dalong shales are low. The shales have diverse types of pores. Shale porosities range between 1.2 and 7.8% (averaging 3.13%). The horizontal permeability of the shale reservoir intervals varies between 0.002 and 335.209 mD (averaging 23.785 mD). Bubble-like and elliptical organic pores are the most developed, mostly occurring as micropores and mesopores <50 nm in diameter. Non-organic pores account for only a small proportion of the total porosity, mainly including intraparticle dissolution pores and interparticle pores; some interparticle pores are well interconnected. Organic marginal contraction, diagenetic, and structural fractures are also developed. Brittle minerals in the shales resist compaction, preventing the collapse of organic pores. (3) Mesopores in the Dalong siliceous shales dominate the total porosity, accounting for 68.9% of the total pore volume. The contributions of micropores and macropores to porosity are subordinate, although micropores contributed the most to the specific surface area, accounting for 61.2% of the total specific surface area (compared to 38.6% for mesopores). The pore volumes and specific surface areas of the shales are positively correlated with clay and organic matter contents and weakly negatively correlated with quartz and carbonate mineral contents. The pore structure of the Dalong Formation shales was influenced by organic matter and clay mineral contents. (4) The Dalong siliceous shales have a strong methane adsorption capacity, which is positively correlated with the volumes and specific surface areas of micropores and mesopores, as well as clay mineral content, and strongly positively correlated with TOC content. These findings demonstrate that Dalong siliceous shales with higher organic carbon contents have more developed micropores and mesopores, larger pore volumes and specific surface areas, and stronger methane adsorption capacities. \begin{table}
\begin{tabular}{l c c c c c c c c c c} \hline \hline
**Sample** & **Depth** & **TOC** & **\(R_{\rm o}\)** & **Quartz** & **Clay** & **Carbonate** & **Total** & **Micropore** & **Mesopore** & **Mesopore** & **Mesopore** \\
**Location** & **Depth** & **(wt. \%)** & **(\%)** & **(\%)** & **(\%)** & **(\%)** & **(\%)** & **(10\({}^{-2}\) cm\({}^{2}\)/g)** & **Volume** & **Volume** & **Gas Content** \\
**Woodford** [56] & 3721 & 2.0 & 1.51 & 32.0 & 45.8 & 10.1 & 4.7 & 0.6 & 1.9 & — \\ Barnett [56] & 1957 & 3.2 & 2.25 & 46.7 & 36.3 & 7.8 & 3.0 & 0.4 & 1.3 & — \\ Longmaxi & & & & & & & & & & \\ Formation in eastern & & & & & & & & & & \\ Sichuan [49] & & & & & & & & & & \\ Dalong & & & & & & & & & & \\ Formation in Western Hubei & & & & & & & & & & \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Shale reservoir characteristics of the Dalong Formation in Western Hubei compared to other typical shale reservoirs. (5) Compared to shale gas reservoirs in other regions, the siliceous shales in the Western Hubei Dalong Formation have high organic matter contents, high brittle mineral contents, good storage conditions, and high desorption gas contents. In conclusion, the Dalong Formation in Western Hubei is characterized by superior hydrocarbon generation conditions, good storage conditions, and lithologies favorable to later hydraulic fracturing. Conceptualization, K.D. and T.X. ; methodology, K.D., Y.W. and Y.L. ; investigation, K.D., T.X., Y.W., Y.Z., W.S. ; resources, K.D., T.X., Y.W. and Y.Z. ; writing--original draft preparation, K.D.