This study addresses the complex structural controls and heterogeneous fracture networks inherent in the fractured basement reservoirs of the Cuu Long Basin. We implemented an Improved Halo Model (IHM) specifically for the SN basement reservoir by integrating multi-type fault classification with spatial parameters, including horizontal distance-to-fault (DTF) and vertical distance from the top of basement (DTOB), alongside block-specific calibration. All critical inputs—ranging from fault architecture and DTF/DTOB volumes to porosity–depth trends—were derived directly from rigorous seismic interpretation and well-log analysis. Our findings reveal that Type 1 and Type 2 faults are the primary drivers of porosity enhancement. In these zones, near-fault porosity reaches 10–14%, contrasting sharply with the 2–5% observed in distal, weakly fractured areas. We noted a significant vertical attenuation effect, where porosity drops abruptly within the first 50–100 m below the basement top before reaching a stable baseline at greater depths. Furthermore, horizontal attenuation coefficients vary across different fault types and structural blocks, reflecting the influence of tectonic uplift and fracture connectivity. The IHM-based permeability modeling highlights strong anisotropy, identifying high-permeability corridors (tens to hundreds of millidarcies) concentrated in the SNN block, while the SN-4X block exhibits much lower continuity. Validation against log-derived data confirms that the IHM significantly outperforms the classical Halo Model by reducing overestimation in deeper intervals and accurately capturing structural constraints. This workflow successfully reconstructs the 3-D distribution of reservoir quality and offers a reliable framework for evaluating other crystalline basement reservoirs within the Cuu Long Basin and similar tectonic settings worldwide.