Abstract
<title>Abstract</title> <p>The shale of the Lower Longmaxi Formation in the Zigong area is stable and serves as the core layer for shale gas exploration and development in this region. Studying the development characteristics of shale fractures is crucial for understanding the enrichment and accumulation of shale gas, as well as for subsequent development and design. This research, based on outcrop, core, well logging and seismic data, identifies the types of fracture development in the Lower Longmaxi Fm shale in Zigong and relates these fractures to the region’s structural system. Fractures developed in the Zigong block strike mainly northeast, S-N, northwest and E-W, and their development is mostly related to compressive stress. The NE-trending and near S-N-trending fractures are a group of conjugate shear fractures formed by early NW-trending compressive stress. The NW-trending and EW-trending fractures are a group of conjugate fractures formed under the constraint of early NE-trending structures under the influence of the continuous NE-trending compressive stress since the Oligocene. Fracture density is greatest near faults, around fold crests, and around the upper parts of fold limbs. Based on fracture identification and simulation of in-situ stress, development models for fractures around single thrusts, back-thrusts, oppositely dipping thrusts, vertical strike-slip faults, and imbricate, "Y"-shaped, anti-"Y"-shaped, semi-flower-shaped and flower-shaped structures are established. Favourable areas for fracture development in the study area are then predicted. Fractures in the Zigong area are mainly developed near NE-trending faults, and structural highs are densely developed. The fracture development models established in this study can provide valuable insights for the identification of fracture development characteristics in similar geological settings.</p>