Abstract:

Located in the complex structural area of the southeastern margin of Sichuan Basin, Nanchuan area is characterized by the prevalent development of low-level reverse faults. This study employs a combination of regional structural analysis and fine structural interpretation to explore the formation mechanisms and distribution patterns of these reverse faults. Utilizing seismic fracture-attribute prediction, drilling, fracturing, and gas test data, this research analyzes the impact of low-level reverse faults on shale reservoir performance, preservation conditions, and fracturing transformation, with a specific focus on the Pingqiao Dong-1 Fault. Findings indicate that the formation of lower-level reverse faults in the Nanchuan area, predominantly oriented NE and NNE with a small scale, was mainly influenced by the long-distance transmission of intracontinental orogeny from the Jiangnan-Xuefeng uplift and changes in the regional compressional tectonic stress field during the Middle to Late Yanshan periods. The Pingqiao Dong-1 Fault notably enhances reservoir properties through the presence of abundant natural fractures without compromising the preservation conditions. This fault alignment facilitates hydraulic fracturing processes to form complex fracture networks, leading to high production from individual wells. Further, exploration and development practices demonstrate that shale gas wells located within 400 meters of lower-level reverse faults achieve high yields, identifying these vicinities as favorable zones for target optimization and well deployment. The results from this study offer valuable insights and guidance for the exploration and development of shale gas in structurally complex regions.

Key words: Nanchuan area, Pingqiao Dong-1 Fault, lower-level reverse fault, shale gas, enrichment and high yield