Experimental Study on Hydraulic Fracture Propagation Mechanism of Water Injection Propagation in Super Deep Fracture-Cavity Carbonate Reservoir

The super deep fracture-cavity carbonate reservoir in Tarim Basin has copious amounts of oil and gas, in which karst cave is the main reservoir space. It is necessary to communicate with karst cave through hydraulic fractures to realize efficient development due to the deep burial, poor physical properties, random distribution of natural fractures and caves, complex location relationship between wells and caves. Therefore, it is of great significance to study the hydraulic fracture propagation mechanism in fracture-cavity carbonate reservoir. In this research, a novel laboratory simulation method for water injection propagation was established based on true tri-axial hydraulic fracturing equipment. Using this method, the law of fracture connecting cave under different experimental conditions were analyzed, and the relationships between water injection volume and cave volume were clarified. The results show that: low stress difference, small included angle (between cave and horizontal maximum stress) and the use of temporary plugging agent have huge contribution to improve the number of caves that connected with hydraulic fractures; the critical turning condition of hydraulic fracture is sensitive to factors such as the position relationship of well and cave, horizontal stress difference and included angle. This study has certain theoretical guiding significance for fracturing design and water injection parameter optimization in fracture-cavity carbonate reservoir.