Experimental Investigation of Simultaneous and Asynchronous Hydraulic Fracture Growth from Multiple Perforations in Shale Considering Stress Anisotropy

Shale oil and gas economic exploitation depends closely on effective hydraulic fracturing stimulations. However, due to the reservoir heterogeneity and in-situ stress variation, the hydraulic fracturing through multiple perforations in shale is confronted with imbalanced fracture growth. To investigate, we reported a new laboratory study that simulates hydraulic fracturing through multiple perforations in shale blocks. The effect of horizontal in-situ stress difference on simultaneous and asynchronous fracture growth from spiral perforations was analyzed. The results show that the in-situ stress difference significantly influences hydraulic fracture initiation and growth, fluid pressure behavior, and fracture orientation. Under a high value of horizontal in-situ stress difference, parallel transverse fractures are initiated simultaneously and growing independently along the direction of σ H . Higher injection pressure is required to promote hydraulic fracture propagation with the decrease of horizontal in-situ stress difference. The induced fractures grow asynchronously from two adjacent perforations and later merge into a large tortuous fracture. Besides, the azimuth angle of hydraulic fracture deflects from the direction of σ H , and the inclination angle gradually decreases. When the value of σ h is close to σ H , an inclined longitudinal fracture and multiple mini-transverse fractures are created from spiral perforations, resulting in a prolonged fracturing process and a significant near-wellbore fracture complexity.