Fracturing behavior of tight sandstone containing hollow double-wing crack (HDWC) under microwave irradiation

As an emerging rock-breaking technology, microwave irradiation has demonstrated significant potential as an auxiliary technique for volume stimulation in hydraulic fracturing. This study focuses on tight sandstone gas extraction, introducing a hollow double-wing crack (HDWC) configuration into the research on tight sandstone. Laboratory experiments were conducted to investigate microwave-induced fracturing mechanisms and the mechanical behavior of HDWC-containing sandstone, aiming to elucidate the thermal cracking patterns and underlying mechanisms under microwave irradiation conditions. To further explore the electromagnetic-thermal-mechanical (E-T-M) interactions in tight sandstone under microwave treatment, a coupled finite element method (FEM)-discrete element method (DEM) numerical model was developed. This model enabled a detailed analysis of force chain evolution and microcrack propagation within HDWC-containing sandstone. Additionally, preliminary hydraulic fracturing simulations were performed to investigate fracture initiation pressure and fracture evolution following microwave exposure. The main findings of this study are as follows: (1) Microwave heating induces thermal cracks at both the tips and midsections of the HDWC. Microwave irradiation degrades the mechanical properties of HDWC-containing sandstone. (2) Simulation results reveal that significant stress concentration and tensile-compressive zoning occur near the HDWC under microwave irradiation. Microcrack development exhibits an avalanche effect. (3) Hydraulic fracturing simulations indicate that microwave heating generally promotes hydraulic fracture generation. Microwave irradiation reduces the fracture initiation pressure and enhances the complexity and connectivity of the fracture network. These findings provide valuable insights into the application of microwave-assisted volume stimulation as a supporting technology for hydraulic fracturing in deep reservoirs.