Mechanism of hydraulic fracture propagation and deflection in the vicinity of normal fault

Due to the influence of faults, the distribution of the in situ stress field in the reservoir is uneven, which affects the fracture propagation behavior during hydraulic fracturing and subsequently affects the reservoir production increase effect. This study systematically analyzes the influence of fault characteristics on hydraulic fracture propagation using numerical simulations to optimize fracturing designs and reduce geological disaster risks. Focusing on normal faults, four key parameters were selected: elastic modulus ratio (KE), fault dip angle (FD), fault thickness (FT), and vertical distance from the wellbore to fault (VD). A seepage-stress-damage coupling model was used to investigate the influence of these four key parameters on hydraulic fracture propagation. Results show that when VD is less than 25 m, fracture propagation is significantly affected by fault stress disturbance, with deflection angles reaching up to 27°. When VD exceeds 40 m, fracture propagation returns to being controlled by the maximum principal stress direction. Fracture deflection is significant when KE is below 0.3 but diminishes when KE exceeds 0.35. FD produces the maximum deflection angle at 45°, while the stimulated reservoir area (SRA) reaches its maximum at 60°. Increased fault thickness reduces the stress disturbance range and the risk of fault reactivation. These findings provide parameter guidance for optimizing hydraulic fracturing designs and reducing risks in faulted reservoirs.