Characteristics of pre-Paleogene faults and their petroleum geological significance in the Chengdao area of Shengli exploration region

Based on detailed interpretation of 3D seismic data and drilling data, this study systematically explores the developmental characteristics of pre-Paleogene faults in the Chengdao area using refined geometric structural analysis and balanced cross-section techniques. It also deeply analyzes their controlling effects on buried hill reservoirs, traps, and the hydrocarbon accumulation process. The research results show that the dominant faults in the Chengdao area include the Chengbei Fault, Chengbei 20 Fault, and Chengbei 30 Fault. As the main controlling faults of the buried hills, they divide the Chengdao buried hills into three major regions: the West Row of Hills, the Middle Row of Hills, and the East Row of Hills. Moreover, during the Yanshanian period, the Middle Row of Hills and the East Row of Hills were influenced by the sinistral strike-slip of the Tan-Lu Fault Zone, resulting in the development of a series of NNE-trending strike-slip faults that further divided the buried hills into north-south trending strips. The nearly EW-trending reverse extension faults exacerbated the structural complexity, forming a complex east-west fault-block structural pattern in the buried hills. According to structural styles and stress field characteristics, the Chengdao buried hill area can be divided into an extensional tectonic zone, a transtensional tectonic zone, a transpressional tectonic zone, and a strike-slip tectonic zone. The main faults in the Chengdao area control the overall evolution of the buried hill structure, while secondary faults determine the formation and distribution patterns of traps. In addition, differences in fault activity are the main controlling factors for the differential enrichment of hydrocarbon reservoirs in the buried hills of the Chengdao area. The range of fracture activity controlled by large-scale and active faults is roughly between 270-350 m. The intensity and duration of fault activity are positively correlated with the development degree of weathered crust and fractured reservoirs. Overall, the buried hills in the Chengdao area exhibit hydrocarbon geological characteristics of multiple hydrocarbon sources and segmentation by major faults.