## 4 Experimental Results  
### Organic Petrological Characteristics  
The results of organic matter microcomposition show that the Permian hydrocarbon source rocks in Northeast Sichuan differ greatly in different layers of the Dalong, Wujiaping and Maokou Formations, reflecting the different sources of organic matter. The specular groups in the hydrocarbon source rocks are less developed and are mainly dominated by the corrosive mud groups, with a very small amount of chitinous and inert groups. Based on the casein carbon isotope study, the previous researchers concluded that the organic matter type of Dalong Formation shale is dominated by II\({}_{2}\)-III type, i.e., the main body is the humic type, which is very different from the I-II\({}_{2}\) type of organic matter revealed by the study of [PERSON]. The difference is likely to be due to the fact that casein carbon isotope is affected by the combination of various factors, such as the hydrocarbon parent material and the degree of thermal evolution of the organic matter. However, there is a huge difference in hydrocarbon potential between humic and saprophytic organic matter. However, in recent years, great discoveries of shale oil, shale gas, dense sandstone gas and coal bed methane have been made in the exploration of the Dalong Formation of the Upper Permian in Northeastern Sichuan, which also confirms that the Permian shale in Northeastern Sichuan has the potential to produce hydrocarbons, which laterally reflects that the organic matter is the humus type. The abundance of putrescible amorphous bodies suggests that the Late Permian Orogeny mainly received organic matter inputs from planktonic algae and lower microorganisms in the water column, and that the algal bodies were basically degraded to putrescible amorphous bodies by bacteriolysis during the early stages of sedimentary diagenesis [60; 61; 62; 63]. Sample X-1 is a core sample of shale from the Dallon Formation at a depth of 4213.35 m, photographed under reflected light from a 5\(\times\) lens, with large pieces of faunal debris visible in the sample (Figure 2a). Samples X-4 are core samples of shale from the Dalong Formation at a depth of 4229.1 m, photographed under reflected light from a 10\(\times\) lens, with foraminifera and some faunal debris visible in the samples (Figure 2b). Sample X-13 is a core sample of shale from the Dallon Formation at a depth of 4266.23 m, photographed under reflected light from a 50\(\times\) oil lens, with solid bitumen and large amounts of pyrite visible (Figure 2c). Sample X-15 is a core sample of shale from the Dallon Formation at a depth of 4270.39 m, photographed under reflected light from a 50\(\times\) mirror oil lens, which shows a lot of pyrite and a lot of organic matter (Figure 2d). Samples X-19 are core samples of shale from the Wujiaping Formation at a depth of 4297.28 m. Photographs under reflected light from a 50\(\times\) oil lens show a large amount of organic matter, mainly solid asphalt specks and filaments as well as many granular pyrites (Figure 3a). Sample X-22 is a core sample of shale from the Wujiaping Formation at a depth of 4310.39 m, photographed under reflected light from a 50\(\times\) oil lens, rich in organic matter, mainly solid asphalt, with a small amount of specularia, and a large amount of pyrite is visible (Figure 3b). Samples X-20 are core samples of shale from the Wujiaping Formation at a depth of 4297.28 m. Photographs under reflected light from a 50\(\times\) oil lens are rich in organic matter, with predominantly mirrored bodies and solid asphalt, as well as a small amount of filamentous bodies (Figure 3c). Sample Y-7 is a core sample of shale from the Wujiaping Formation at 3324.38 m, photographed under reflected light from a 50\(\times\) oil lens, with high organic matter content and large amounts of solid bitumen visible (Figure 3d).