The Shahejie Formation in Nanpu Sag is a crucial region for deep-layer hydrocarbon exploration in the Bohai Bay Basin. To address the impact of faults on sublacustrine fan formation and spatial distribution within the study area, this study integrated well logging, laboratory analysis, and 3D seismic data to systematically analyze sedimentary characteristics of sandbodies from the first member of the Shahejie Formation (Es₁) sublacustrine fans, clarifying their planar and cross-sectional distributions. Further research indicates that Gaoliu Fault activity during Es₁ deposition played a significant role in fan development through two mechanisms: (1) vertical displacement between hanging wall and footwall reshaped local paleogeomorphology; (2) tectonic stresses generated by fault movement affected slope stability, triggering gravitational mass transport processes that remobilized fan delta sediments into the central depression zone as sublacustrine fans through slumping and collapse mechanisms. Core observations reveal soft-sediment deformation features, including slump structures, flame structures, and shale rip-up clasts. Seismic profiles show lens-shaped geometries with thick centers thinning laterally, exhibiting lateral pinch-out terminations. Inverse fault-step architectures formed by underlying faults control sandbody distribution patterns, restricting primary deposition locations for sublacustrine fan development. The study demonstrates that sublacustrine fans in the study area are formed by gravity flow processes. A new model was established, illustrating the combined control of the Gaoliu Fault and reverse stepover faults on fan development. These findings provide valuable insights for gravity flow exploration and reservoir prediction in the Nanpu Sag, offering important implications for hydrocarbon exploration in similar lacustrine rift basins.

In recent years, major breakthroughs have been achieved in oil and gas exploration within China’s complex thrust–fault zones in the western region, confirming their significant potential. The northern piedmont zone of the Turpan–Hami Basin, a classic thrust–fold belt formed by the Bogda Orogenic belt’s overthrusting, has seen the discovery of several Jurassic–Cretaceous hydrocarbon fields, yet exploration at its thrust-front margins remains relatively underdeveloped. This study focuses on the central piedmont segment at Qialekan and Kekeya, integrating 3D seismic data with fault-related folding theory and balanced cross-section restoration to systematically analyze the area’s tectonic evolution. We specifically examine the formation and modification of wedge structures and assess their petroleum geological significance. Our results indicate that the wedge bodies formed in the Late Jurassic, along with their subsequent basinward insertion, critically controlled the present-day structural framework. In the Qialekan area, wedge formation coincided with the main hydrocarbon expulsion phase of underlying Permian source rocks. Type I faults acted as effective migration pathways, while later tectonic reworking was limited, favoring for hydrocarbon preservation. In contrast, in the Kekeya area, wedge structures underwent intense modification by Type II faults, which pierced the wedge and facilitated vertical hydrocarbon migration, creating a mixed-source accumulation pattern. The findings of this study provide new theoretical insights and practical guidance for future exploration in the northern piedmont zone and also offer a valuable reference for hydrocarbon exploration in structurally similar foreland basins.

The Tazhong No. 2 fault zone is a major fault zone in the Tazhong area, and studying its structural characteristics is of great significance for hydrocarbon exploration. Based on detailed structural interpretation of 2D and 3D seismic data, this study suggests that the Tazhong No. 2 fault zone exhibits distinct segmented deformation characteristics and can be divided into four segments along strike, with the individual structural segments bounded by NE-trending strike-slip faults. The eastern and western parts of the Tazhong No. 2 fault zone differ in their evolutionary characteristics: during the early stage, deformation was intense in the east and relatively weak in the west, whereas during the late stage, the central segment was more active while the eastern and western segments were essentially inactive. Vertically, the fault zone displays stratified deformation: taking the Middle–Lower Cambrian evaporites as the boundary, the suprasalt strata are more strongly deformed than the subsalt strata. The segmented and layered deformation characteristics of the Tazhong No. 2 fault zone are mainly controlled by factors such as the basement structure, the Middle–Lower Cambrian evaporites, and regional tectonic events. Based on the segment-specific accumulation–evolution model, the shallow fault–lithologic traps and volcanic-rock-related traps in the west, the subsalt structural traps, and the buried-hill interior and drape traps are all favorable exploration targets.