Evolution of Stress Fields in Structural Intersection Zones and Its Impact on Fracture Development: A Case Study of Yuanba and Tongnanba Areas in North Sichuan

Tight sandstone reservoirs within tectonic intersection zones are shaped by multi-directional, polyphase stresses that generate fractures of variable density and scale. These structural overprints, superimposed on porosity variations from sedimentary and diagenetic processes, introduce strong heterogeneity, complicating reservoir characterization and prediction. Accurate delineation of fracture networks therefore requires systematic analysis of the geometry, evolution, and genetic mechanisms of intersection zones. By integrating field structural measurements with seismic interpretation, it constrained the spatial architecture of intersection zones and simulated fracture variability across subregions. Stochastic modeling under stress-field constraints captured directional deviations between individual fractures, reflecting the intrinsic randomness of natural systems. Results indicate that during the late Yanshanian, NW-SE directed compression dominated, producing NE-trending folds (Jiulongshan and Tongnanba anticlines) that exerted first-order control on fracture development. In contrast, Himalayan deformation was partitioned: NE-trending faults developed in the western Yuanba area, NS-trending faults in the central Yuanba, and NW-trending faults in the Tongnanba area. While Yanshanian folds primarily governed fracture distribution, Himalayan faults became the dominant control. From west to east, fracture intensity increases, with mechanisms evolving from single-fault control (Yuanba) to more complex fault bending, inflection, and enéchelon arrangements (western Tongnanba), culminating in dense fracture networks generated by intersecting faults in eastern Tongnanba.