## 5 Comparative Analysis of Hydrocarbon Source Rock Indicators
### Hydrocarbon Source Rock Quality  
The Lower Silurian hydrocarbon source rocks of North Africa, the Middle East, and South China vary in quality and organic matter abundance, but overall, they are considered high-quality hydrocarbon source rocks with distinct characteristics in different regions (Table 2).  
The Lower Silurian hydrocarbon source rocks are well preserved in the Oued Mya Sub-Basin of the Triassic Basin in North Africa. The organic matter is predominantly type I, with a total organic carbon (TOC) content ranging from 3 to 20%, averaging 6%, and a  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Distribution Area** & **Basin** & **Organic Matter Type** & **Organic Carbon Content** & **Hydrogen Index (HI)** \\ \hline North Africa Sahara & Oued Mya Basin & Type I kerogen & 3–20\% & 60 mg/g \\ Platform & Ghadames Basin & Types I and II kerogen & 1–17\% & 600 mg/g \\ Middle Eastern Arabian & Central Arabian Basin & Types I and II kerogen & 1–20\% & Max, 670 mg/g Average, 339 mg/g \\ Platform & Rub’ al Khali Basin & Types I and II kerogen & 2.0–8.65\% & 50–200 mg/g \\ South China Yangzi & Sichuan Basin & Types I/I-II kerogen & 1.29–11.94\% & \\ Platform & \multicolumn{1}{c}{} & & \\ \end{tabular}
\end{table}
Table 2: Comparison of Silurian hydrocarbon source rock characteristics in North Africa–Middle East–South China.  
Figure 10: Photos of the characteristics of the Lower Silurian dark graptolite hydrocarbon source rock in North Africa, the Middle East, and South China. (**a**) Outcrop and core photos of the Lower Silurian black graptolite shale in the Yangtze Platform of South China. (**b**) Outcrop and core photos of the Lower Silurian black graptolite hydrocarbon source rock in North Africa.  
hydrocarbon generation potential exceeding 60 kg/t. In the Ghadames Basin, the organic matter is types I and II, with a TOC ranging from 1 to 17%, derived mainly from lower aquatic algae and bacteria.  
In the Middle East, the Silurian hot shales exhibit types I-II organic matter. The amorphous components in the kerogen microscopic components exceed 60%, primarily derived from gratolites, chitinozoans, marine algae, and organisms with uncertain origins. The TOC generally ranges from 1 to 20%, with an average of 3-5%, and the hydrocarbon generation potential is between 8.0 and 13.5 mg/kg. Specifically, the TOC ranges from 2.0% to 8.65% in the Rub' al Khali Basin. In the Central Arabian Basin, the TOC ranges from 1 to 11%, reaching up to 20%; in the Western Arabian Basin, the average TOC is 5%, reaching up to 16%.  
In the Sichuan Basin of the Yangtze Platform in South China, the Silurian Longmaxi Formation hydrocarbon source rocks are dominated by type I sapropelic organic matter and types I-II organic matter [78]. The TOC ranges from 1.29 to 11.94%, and the organic matter maturation conversion rate can reach approximately 66.7%. In the northeastern Chongqing area, the TOC of the Silurian Longmaxi Formation shale ranges from 0.57 to 4.96%, averaging 2.86%. In southeastern Sichuan, the TOC ranges from 0.7 to 2.29%, averaging 1.50%, and in the northern Guizhou area, the high abundance hydrocarbon source rock of the Longmaxi Formation has a TOC as high as 5.44%.