Multi-cluster fracturing simulation in a naturally fractured sandstone reservoir using a fully coupled hydro-mechanical-damage model

During hydraulic fracturing, complex interactions occur between hydraulic fractures (HFs) and natural fractures (NFs), leading to uncertainty in assessing reservoir stimulation effectiveness; however, the underlying mechanisms are poorly understood. Here, we build a realistic geological model for a fractured sandstone reservoir in the Ordos Basin based on unmanned aerial vehicle photogrammetry. A novel fully coupled hydro-mechanical-damage (HMD) model for large-scale hydraulic fracturing simulation is developed based on Biot’s poroelasticity theory and meso-damage mechanics, enabling efficient and accurate simulation of HF-NF interactions. Numerical simulations of multi-cluster fracturing in a horizontal well based on the geological model are conducted to investigate the influence of rock heterogeneity, NFs, in-situ stress, and injection rate on HF propagation. The results demonstrate that bedding planes, serving as oriented, continuous weak interfaces, guide directional propagation of HFs and increase the complexity of fracture networks. Conversely, randomly distributed joints predominantly induce branching or deflection of the main HFs, dissipating energy into the surrounding rock mass and thereby reducing stimulation efficiency. Differential in-situ stress (Δ σ ) has a strong influence on fracture morphology: low Δ σ promotes random fracture deflection and the formation of complex fracture networks, whereas high Δ σ favors preferential propagation along the maximum principal stress direction, resulting in simplified HF geometries. Results also indicate that rock heterogeneity can influence fracture complexity by modulating dominant propagation pathways and energy distribution. Quantitative analysis indicates injection rate has a substantial impact on stimulation effectiveness. This work advances understanding of geological and operational controls on hydraulic fracture complexity, providing guidance for efficient field-scale fracturing.