**2. Geological Setting**

The northwestern marginal fault system of the Junggar Basin is located in the middle of the Central Asian Orogenic Belt (CAOB) (Figure 1), which is in the coupling region between the Junggar Basin and West Junggar Block. Its formation and evolution were mainly affected by the activity of the West Junggar Orogenic Belt to the west [16]. From north to south, it is divided into the Wu-Xia, Ke-Bai, and Hong-Che Fault Zones [17–20]. The Hong-Che Fault Zone is located at the southern end of the fault system, which is located at the northwestern margin of the Junggar Basin (Figure 1). It strikes nearly north-south and has a length of approximately 80 km and width of approximately 10–20 km. It is adjacent to the Ke-Bai Fault Zone to the north, Chepaizi Uplift to the west, Sikeshu Depression to the south, and the Zhongguai Uplift and Shawan Depression to the east and extends over an area of approximately 1500 km<sup>2</sup> [21,22].

**Figure 1.** Sketch maps. (**a**) The tectonic location of the Junggar Basin in the CAOB. (**b**) Division of tectonic units in the Junggar Basin. (**c**) The major faults in and around the Hong-Che Fault Zone (modified after [23]).

Studies have shown that the West Junggar region was in a post orogenic extensional environment during the Late Carboniferous to Early Permian [24–27]. The Late Carboniferous-Early Permian volcanic rocks in the West Junggar area and surrounding areas are mainly basalts and rhyolites with less neutral components, which form a typical "bimodal" series. A-type granites are well developed. This tectonic rock association and geochemical characteristics indicate that they formed in an extensional environment of crustal thinning. It is comprehensively judged that the study area has a post orogenic extensional background. During this period, the basin was mainly composed of grabens and half grabens, which were controlled by normal faults with a dual structure of "lower faults and upper depressions" [16,27]. Since the Permian, it has experienced five tectonic stages: Early Permian post orogenic extension, strong Middle-Late Permian compression and thrusting, inherited Triassic thrust superimposition, overall Jurassic-Cretaceous oscillation, and Cenozoic intracontinental foreland [16,28].

According to the drilling and seismic data, the Carboniferous, Permian, Triassic, Jurassic, Cretaceous, Paleogene, Neogene, and Quaternary all developed from bottom to top in the study area (Figure 2). The Lower Permian Jiamuhe Formation (P1j), Fengcheng Formation (P1f), Middle Permian Xiazijie Formation (P2x), LowerWuerhe Formation (P2w), and Upper Permian UpperWuerhe Formation (P3w) developed from bottom to top. The Baikouquan Formation (T1b), Karamay Formation (T2k), and Baijiantan Formation (T3b) developed from bottom to top in the Triassic. The Jurassic mainly includes the Badaowan Formation (J1b), Sangonghe Formation (J1s), Xishanyao Formation (J2x), Toutunhe Formation (J2t), and Qigu Formation (J3q). The Tugulu Group (K1tg) developed in the Cretaceous. Since the study area has been located at a high position of structures from the Permian to the end of the Jurassic and has been in a state of continuous uplift for a long period, the Permian and Triassic are missing in most areas of the fault zone. From east to west, the Jurassic and Cretaceous overlapped and were deposited on top of the Carboniferous bedrock. Due to the influence of the late Hercynian, Indosinian, Yanshanian, and Himalayan movements, the unconformity surfaces of the lower boundaries of the Upper Wuerhe Formation (P3w), Jurassic, Cretaceous, and Neogene are developed in the study area.

**Figure 2.** Stratigraphic characteristics of the Hong-Che Fault Zone (modified from [29]).

#### **3. Data and Methods**

The research data includes three-dimensional seismic data of the Hong-Che Fault Zone, well logging, core and casting thin section data of exploration wells. The target layer of study is the Carboniferous volcanic rocks. Through the interpretation of seismic data, we analyze the structural characteristics of the reservoir. Based on the analysis of typical oil and gas reservoirs in the Chefeng 3 and Che 210 well blocks, the main controlling factors and hydrocarbon accumulation model of Carboniferous volcanic rocks in the Hong-Che Fault Zone are obtained.
