关键词: 水力压裂, 岩石, 随机场, 键型近场动力学, 裂隙追踪

Abstract: In order to study the fracture propagation morphology of hydraulic fracturing in heterogeneous rock, the random field theory of the center point method was applied to randomize the physical and mechanical parameters of rock. The surface of newly formed fractures was tracked in real time and pressure was applied to simulate the interaction between fracturing fluid and fracture wall. A numerical model for simulating the hydraulic fracturing process of rock was proposed based on the bond-based peridynamics. According to the compression test results of rock containing a prefabricated crack, the effectiveness of the proposed model was verified, the evolution of rock hydraulic fractures was explored considering the effect of the spatial variation direction of rock elastic modulus, fluctuation range of rock elastic modulus, and perforation spacing. When the distribution of rock elastic modulus is layered, the hydraulic fractures tend to propagate along the weak interfaces. When the parameter distribution is directionless, the expansion of hydraulic fractures exhibits strong randomness, and the fracture network tends to become more complex. When the parameter fluctuation range is small, the variability of rock elastic modulus is significant, which caused stress concentration locally, making it easy to form complex fracture structure. A larger parameter fluctuation range leads to homogenization of rock, and the expansion of hydraulic fractures is singular, resulting in a relatively low fracture propagation rate. Under the action of dual perforation, the expansion of fractures in homogeneous rock exhibits a symmetrical distribution. The perforation pressure suppresses the expansion of fractures between the perforations, leading to the main fractures tending to expand towards the boundaries on both sides. And there is a competitive relationship in the expansion of hydraulic fractures in heterogeneous rock. Under the combined effect of stress concentration and material heterogeneity, one hydraulic fracture preferentially expands and then inhibits the development of another one.

Key words: hydraulic fracturing, rock, stochastic field, bond-based peridynamics, crack tracking