Multi-scale digital rock-based sensitivity evaluation and optimization of stimulation strategies in tight sandstone reservoirs

Reservoir stimulation plays a vital role in enhancing the productivity of tight sandstone formations; however, the injection of stimulation fluids often leads to varying degrees of reservoir damage. Traditional sensitivity evaluations, which rely primarily on laboratory core displacement experiments, can assess overall permeability loss but are limited in revealing the pore-scale mechanisms underlying fluid–rock interactions and their multi-scale effects on reservoir microstructure. To address these limitations, this study introduces a multi-scale digital rock-based methodology that integrates high-resolution imaging and numerical upscaling techniques. Three imaging modalities—plug-scale micro-CT, sub-sample micro-CT, and scanning electron microscopy (SEM) at 500× and 5000× magnifications—were employed to quantitatively analyze changes in pore structure and permeability before and after five types of sensitivity tests: rate, water, salt, acid, and alkali sensitivity. Results show that all five sensitivity mechanisms significantly impair permeability, with water and salt sensitivities causing the most severe reductions (up to 68.4% and 69.9%, respectively), mainly due to clay swelling and particle detachment. In acid sensitivity tests, although pore volume increased via mineral dissolution, permeability still declined by 57.1% due to pore-throat blockage from secondary precipitates. Importantly, multi-scale digital rock analysis revealed that microscopic alterations in pore-throat geometry exert a dominant influence on macroscopic permeability trends—an insight not accessible through conventional experimental methods. The proposed approach enables a more quantitative, visual, and mechanism-informed evaluation of sensitivity-induced damage. These findings offer critical guidance for optimizing stimulation fluid design and mitigating formation damage, demonstrating the superior capability of digital rock technology to resolve complex fluid–mineral interactions and inform reservoir management strategies across scales.