Dynamic fracture propagation in hydraulic re-fracturing

Re-fracturing is important for stimulating low-permeability reservoirs, for the effective production duration after the initial fracturing is short and needs to be stimulated again. However, the fracture configuration caused by re-fracturing affects the re-stimulated production greatly. Based on fracture mechanics and hydraulic fracturing theory, a model for dynamic path of fracture propagation during re-fracturing is proposed, and computation shows that stress difference and initiation angle contribute to changes in fracture propagation path. The new fracture changes its direction gradually, until to the direction of the maximum horizontal stress. Horizontal stress difference has great obvious influence on fracture dynamic reorientation, the larger the horizontal stress difference is, the shorter the distance of reoriented fracture away from the maximum horizontal stress will be. The predicted paths are in good accordance with those from the surface micro-seismic monitoring and tri-axial large-scale experiments. The model and conclusions are significant to further understanding of re-fracturing process.