## 4 Structural Control Mechanisms on Coal and Gas Occurrence in Mines  
### Structural Evolution and Gas Generation  
To further explain the relationship between the structural evolution of coal-bearing strata and coal seam gas generation and dissipation in different mining areas on both limbs of the Kaiping syncline, PetroMod 1D (2012.2) software was used to simulate and reconstruct the structural burial history, thermal evolution history, and hydrocarbon generation history of coal-bearing strata in different mines on both limbs of the Kaiping syncline. The burial history of coal-bearing strata in different mines on the two limbs of the Kaiping syncline is shown in Figure 7. This burial history was compiled based on lithological data, stratigraphic layering, and thickness from actual exploration drilling records in the mining area, as well as stratigraphic development and thickness data from the northern North China Basin. This history also accounts for the timing and extent of uplift and erosion during several key tectonic periods in the northern North China Basin [23; 24; 25]. The burial history curve of the Late Paleozoic coal seams in the Kaiping syncline forms a \"V\" shape, with a turning point in the Late Indosinian period. Combined with the hydrocarbon generation evolution of the coal seams, it shows that the Kaiping coalfield strata began to subside from the Late Carboniferous until the Middle Triassic, when the coal seams reached their maximum burial depth of approximately 3300 m. During this time, the coal seams were heated, generating large amounts of methane (first gas generation). Most  
Figure 7: Burial–hydrocarbon history of the Kaiping oblique coal seam (according to [PERSON] and [PERSON], 2023, modification [26]). (**a**) Sedimentary and burial history diagram of the Kaiping syncline; (**b**) “Three Histories” configuration diagram of the Kaiping syncline. Notes: C: Carboniferous; P: Permian, T: Triassic; J: Jurassic; K: Cretaceous; E: Paleogene; N: Neogene. of the methane dissipated into the surrounding rock, while some remained adsorbed in the coal seams. Subsequently, crustal uplift caused the previously adsorbed gas to dissipate. After the Triassic, tectonic activity intensified, gradually forming the Kaiping syncline. This was accompanied by regional magmatic activity, which reheated the coal seams, leading to secondary gas generation and replenishing the coal gas, primarily in adsorbed and free states. As the crust continued to uplift, the gas in the coal seams gradually dissipated, eventually reaching its present state (Figure 7). Controlled by regional tectonic evolution, the coal-bearing strata underwent a sequence of structural burial, thermal evolution, and hydrocarbon generation processes. Subsequent preservation conditions determined the final characteristics of gas occurrence in the coal. By analyzing the stratigraphic composition of coal-bearing formations, the characteristics of coal seams and roof and floor rock layers, and the evolution of the \"three histories\", the dynamic changes in coal seam gas generation, occurrence, and migration were quantitatively assessed. This enabled an assessment of the geological controls on gas accumulation, as well as an analysis of the entire process of gas generation, occurrence, accumulation, and dissipation in the main coal seams of the study area. Figure 7 illustrates the configuration of the \"three histories\" in the Kaiping syncline, divided into five stages. The first stage, from the Late Carboniferous to the Early Triassic (initial stage of gas generation), involved the slow subsidence of the crust in the Kaiping coalfield during the Hercynian and Indonesian movements, forming stable coal-bearing strata. The coal seams and dark mudstone laid the foundation for coalbed methane, but hydrocarbon generation during this stage was weak. The second stage, during the Triassic (deep burial and gas enrichment stage), saw intensified subsidence due to the Indonesian movement.