Hydraulic fracturing techniques are commonly used to enhance the production of tight reservoirs. Generally, the effect of hydraulic fracturing can be appraised through hydraulic fracturing experiments in the laboratory, in which acoustic emission (AE) is often used to monitor the fracturing process. At present, the number of AE events and spatial distribution of AE locations are the two main factors commonly considered in hydraulic fracturing effectiveness evaluation. However, these commonly used evaluation methods overlook two crucial aspects: the connectivity among fractures and the tensile and shear properties of fractures induced by hydraulic fracturing. In this technical note, we consider the influence of these two previously overlooked aspects on the evaluation of hydraulic fracturing effectiveness by establishing a connected fracture model using AE data. The proposed approach links up AE events based on their spatio-temporal relationship and builds a fracture network called the connection model. Then, the characteristic of the fracture network is represented by the fractal dimension to reveal the complexity of fractures in the network. We extract the tensile-shear properties of each fracture based on the inversion of AE events’ focal mechanism. Finally, based on the pre-known fracturing effectiveness of a fracture network, we compare the connection model of AE events in several triaxial hydraulic experiments. Our findings indicate that a comprehensive evaluation of hydraulic fracturing effectiveness can be achieved by considering both the connectivity of AE locations and the tensile-shear properties of AE events. This work aims to provide a more rational method for characterizing rock fracture networks and evaluating rock fracturing effects using AE data.

Hydraulic fracturing is crucial for extracting shale oil and gas. This technique involves creating fractures in rock formations to enhance reservoir development efficiently. Due to the complexity of shale rock, it is important to conduct multiscale investigations into the fracturing process. Despite extensive research, the technology for deep-underground shale hydraulic fracturing continues to advance as it moves deeper underground. This paper explores the existing technical challenges of shale fracturing, review the current status of physical experiments and numerical simulations, and highlight the importance of multiscale numerical simulation methods. Meanwhile, an integrated approach to optimizing fracturing designs for field cases is introduced. Finally, this paper summarizes the challenges and opportunities in shale hydraulic fracturing, aiming to provide fresh insights into the advancements of hydraulic fracturing technology.