Width of stress disturbed zone near fault and its influencing factors

3D normal fault models in a triaxial crustal stress state were established in finite element simulation software to study the characteristics of in-situ stress in the fault developed areas. Simulated data show that the disturbed zones of in-situ stress widely exist in the surrounding rocks due to the fault movement. The principle stress direction in the disturbed zones is obviously deviated from the background stress state. The stress value is lower near the middle of the faults, while the fault ends are the abnormally high stress realm. Based on the analysis results, the distribution of stress disturbed zone is mainly decided by the fault scale. Width of stress disturbed zone proportionally goes up as fault length and displacement increase simultaneously. Rock mechanism, fault strike, shape of fault plane and background stress state affect the width of stress disturbed zone by changing the ratio of width to fault length (W-L). More intensely fractured fault rock along with higher angle between fault strike and background maximum horizontal principle stress direction, greater ratio of fault displacement to fault length (D-L), larger differential stress, leads to higher W/L value. The conclusions are verified in BZ-X Oilfield, Bohai Bay Basin. Building a 3D geologic model on the basis of actual structure relief and regional stress state, the in-situ stress in 2^nd member of Shahejie Formation was calculated with the finite element method. The distribution of stress disturbed zones near faults is made clear by analyzing variation of in-situ stress state in surrounding rocks. The width of stress disturbed zones changes regularly as predicted in the law above. Both stress value and orientation, is notably changed in disturbed zones, which could affect artificial fracture propagation and well pattern deployment significantly.