## 2 Geological Setting  
The Kuqa Depression, situated on the northern margin of the Tarim Basin, is a foreland basin that has been developing since the late Permian and encompasses approximately 28,000 km\({}^{2}\) (Figure 1a,b). It has experienced significant geological transformations and is characterized by multiple evolutional stages, including a foreland basin stage from the Late Permian to the Triassic, an extensional rift stage from the Jurassic to the Paleogene, and a rejuvenated foreland basin stage since the Neogene [11; 12]. The intensive tectonic deformations and various depositional environments from the Neogene to the Quaternary  
Figure 1: Location maps of (**a**) the Tarim Basin and (**b**) the Kuqa Depression. (**c**) Distribution of the four structural zones and (**d**) a present section through the TD-2 well from north to south in the eastern Kuqa Depression. YT-1 (P) and TG-6 (P) refer to the projection position of the YT-1 well and TG-6 well in this section. DSZ = deep sag zone, SSZ = southern slope zone, CAZ = central anticline zone, NSZ = northern slope zone, Q = Quaternary, N\({}_{2}\)k = Kuqa formation, N\({}_{1}\)j = Jidike formation, E = Paleogene, K = Cretaceous, J\({}_{2}\)kz = Kezilenuer formation, J\({}_{1}\)y = Yangxia formation, J\({}_{1}\)a = Ahe formation, T\({}_{3}\)h = Huangshanjie formation, T\({}_{3}\)t = Taliqike formation, T\({}_{2,3}\)k = Kelamayi formation, Pt = Proteerozoic, C = Carboniferous, O = Ordovician, C = Cambrian.  
form a complex structural pattern, which shows the characteristics of segmentation horizontally and stratification vertically [13]. The basin comprises four belts and three sags, namely, the Northern tectonic belt, the Kelasu and Qiulitage tectonic belts, and the southern slope region from north to south, with the Wushi, Baicheng, and Yangxia sags developed between the tectonic belts from the west to east [14; 15; 16].  
The eastern Kuqa Depression mainly includes the middle-eastern section of the Northern tectonic belt, the Yangxia sag and its surrounding areas, with an area of 7000 km\({}^{2}\), which can be further subdivided into four zones, namely, the northern slope zone (NSZ), the central anticline zone (CAZ), the southern slope zone (SSZ), and the deep sag zone (DSZ) from north to south [17] (Figure 1c). Affected by Yanshan (during the Late Jurassic to the Early Cretaceous) and Late Himalayan (in the Neogene) orogenic movements, the Kuqa Depression has experienced intensive lateral extrusion, especially in the mountain front, forming several large thrust belts (e.g., the Yiqikelike and Tugerming thrust belts) [18; 19].  
Source rocks in the eastern Kuqa Depression mainly developed in the Triassic and Jurassic formations, including an oil-prone lacustrine mudstone deposited in shallow to semi-deep lacustrine settings--as represented by the Upper Triassic Huangshanjie formation--and gas-prone coaly source rocks in paludal to lacustrine settings, as represented by the J1y and J2 kz formations [16]. The source rocks mainly comprise mudstones with several interbedded carbonaceous mudstones and coal-thin seams. At present, the maturity of the source rocks is in a range of 0.6-1.5% R\({}_{0}\)[20; 21]. Thick and tight sandstone reservoirs primarily developed in the J1a and J1y formations and are dominated by medium and coarse sandstones and thin-bedded conglomerates. The property of tight sandstone reservoirs is recognized as ultra-low porosity and low permeability, with limited reservoir space mainly comprising the intra-granular pores, dissolved pores and micro-fractures [22]. The thick gypsum-salt rocks of the Jidike formation are regional seal rocks, and the thick mudstones of the Middle-Upper Jurassic are direct seal rocks. Source rocks, reservoirs, and seal rocks developed interbedded, forming several favorable source-reservoir-seal combinations.