## 5 Discussion
### Petroleum-Geological Implications  
Integrated analysis of lithological characteristics derived from multiple boreholes, outcrops, and seismic interpretations reveals two predominant reservoir assemblages within the Huangshanjie and Kelamayi formations in the study area. Regional studies confirm substantial hydrocarbon generation potential for the Triassic lacustrine source rocks in the Kuqa Depression, characterized by high organic carbon enrichment, suitable thermal maturity, and extensive distribution, providing an ample material foundation for large-to-medium gas accumulations [71; 72; 73; 74; 75]. Figure 13: Triassic sedimentary facies, paleocurrent and paleogeomorphology superposition in Wushi Depression. Reservoir analysis indicates that the Huangshanjie Formation in the southern study area exhibits diverse pore systems, including dissolution pores, intergranular pores, and structural fractures observed in borehole thin sections. Significant lateral heterogeneity exists within this unit: Well YL2 in the south displays well-developed dissolution and intergranular pores with apparent porosity reaching 10%. Progressing northward to Wells ST1 and SM1, intensified calcareous cementing reduces pore volume substantially, shifting pore types toward predominantly structural fractures. This spatial variation partially reflects burial depth controls on reservoir quality. Overall, Triassic sand bodies exhibit adequate reservoir capacity, qualifying as targets for substantial hydrocarbon accumulations. Core analyses from Well ST1 reveal severe calcite cement (Figure 14d), with effervescent calcite veins upon hydrochloric acid application visible in core samples (Figure 6f), suggesting that deep central foreland reservoirs may be compromised by high-salinity fluids resulting in inferior reservoir properties. Sedimentary analysis by [PERSON] et al. of the central Kuqa Depression demonstrates that the coarse-grained conglomeratic units (clast diameter > 10 cm) developed in Members 1 and 3 of the Huangshanjie Formation directly overlie thick, dark mudstones [39]. This abrupt shift to coarse sedimentation responds to a dramatic increase in basin-mountain relief driven by Indosinian tectonic uplift in the provenance area. Conversely, the sharp lithological transition at the top of Member 1/3 to fine-grained deposits (particularly the transition from Member 1 to the dark shale of Member 2) records a rapid lake-level rise triggered by regional lacustrine transgression. This depositional sequence led to the widespread sealing of the early high-porosity and permeability conglomeratic bodies by overlying dense, fine-grained sediments. Consequently, a vertically coupled system formed, comprising the underlying conglomerate reservoir and the overlying mudstone/shale seal. Figure 14: Photomicrographs (10\(\times\) plane-polarized light, PPL) of epoxy-impregnated thin sections from southern Wushi Sag wells, demonstrating the three dominant pore types within the Triassic Huangshanjie Formation and their implications for reservoir quality. Pore spaces are stained blue; calcite cement is stained red. (**a**) Well YL2, 5599.3 m, Huangshanjie Formation. (**b**) Well YL2, 5599.7 m, Huangshanjie Formation. (**c**) Well ST1, 6801.95 m, Huangshanjie Formation. (**d**) Well SM1, 5376.2 m, Huangshanjie Formation. This configuration constitutes an efficient hydrocarbon accumulation unit integrating source rock, reservoir, and caprock, establishing the critical structural foundation for hydrocarbon enrichment within this stratigraphic interval. The Huangshanjie Formation in this study area exhibits analogous sedimentary characteristics, indicating its potential as a similarly efficient accumulation unit capable of hosting large-scale hydrocarbon reservoirs. Research by [PERSON] et al. on the structural styles and their control on hydrocarbons in the Wushi Sag, utilizing geochemical evidence, identified that the hydrocarbons in the Cretaceous reservoir of Well WC1 originated from lateral migration of underlying Mesozoic source rocks [76].