Structural evolution and reservoir-control mechanisms of ultra-deep strike–slip fault zones in the Fuman area, Tarim Basin, China

The discovery of ultra-deep strike–slip fault–controlled hydrocarbon reservoirs in the central Tarim Basin has renewed interest in the structural evolution and reservoir-controlling mechanisms of intracratonic strike–slip systems. Based on integrated drilling data, high-resolution 3D seismic reflection interpretation, and structural analog modeling, this study investigates the F I 12 and F I 17 fault zones in the Fuman area as representative examples. The results show that ultra-deep strike–slip faults exhibit combined lateral segmented growth and vertical stratified propagation, with secondary shear faults overlapping and stepping in both horizontal and vertical directions. To characterize fault activity in a reproducible manner, a semi-quantitative slip intensity framework is established using fault-zone width, structural relief, and segmentation complexity. Comparative analysis demonstrates that slip intensity is the first-order control on the scale and effectiveness of fault-controlled carbonate reservoirs: fault zones with higher slip intensity develop wider damage zones, stronger fracture connectivity, and larger reservoir volumes. Within individual fault zones, slip intensity is preferentially concentrated at lateral step-overs and relay zones of secondary shear faults, where large-scale fracture corridors form and hydrocarbon productivity is significantly enhanced. In addition, for reservoirs characterized by a lower-source–upper-reservoir configuration, hydrocarbon productivity is positively correlated with the proximity of vertical fault step-overs to the target reservoir interval. Shallower vertical overlap facilitates more efficient upward hydrocarbon migration, resulting in higher hydrocarbon abundance. These results establish a three-dimensional structural control model linking slip intensity, fault architecture, and reservoir effectiveness in ultra-deep carbonate strike–slip systems, providing a robust geological basis for reservoir prediction and exploration risk reduction in complex ultra-deep settings.