Mechanisms, Reservoir Responses, and Application Challenges of Microwave-Induced Fracturing for Enhanced Shale Oil...

Microwave-induced fracturing has emerged as a potential water-saving stimulation strategy for improving shale oil and gas recovery. Given the low porosity, low permeability, and strong heterogeneity typical of shale reservoirs, this review critically summarizes the mechanisms, reservoir responses, production implications, and scale-up challenges of microwave-induced fracturing in shale reservoirs. Unlike previous reviews that mainly considered microwave heating as a thermal recovery or oil shale conversion method, this work links dielectric heterogeneity, selective energy deposition, penetration-depth constraints, thermo-mechanical damage, pore-fracture reconstruction, and field implementation into an integrated framework. Microwave energy is preferentially absorbed by water-bearing phases, clay minerals, conductive sulfides, and certain organic components, whereas quartz- and feldspar-rich matrices generally exhibit weaker heating responses. This contrast generates nonuniform thermal fields, thermal expansion mismatch, and localized stress concentration, which may initiate microcracks along mineral interfaces, bedding planes, and preexisting defects. Available laboratory evidence indicates that microwave treatment can enhance pore-fracture connectivity, modify rock mechanical properties, and increase permeability, thereby improving flow capacity and potentially promoting hydrocarbon desorption, viscosity reduction, and organic matter conversion. However, the formation of field-scale complex fracture networks and the resulting recovery improvement remain insufficiently verified. Key technical barriers include limited microwave penetration depth, energy attenuation, water-content and fluid-saturation effects, spatially nonuniform heating, high-power downhole equipment reliability, and uncertain economic feasibility. Future studies should prioritize quantitative energy-efficiency evaluation, field pilot testing, parameter optimization, multiphysics modeling, and integration with hydraulic fracturing, CO₂ injection, or thermal recovery. Overall, microwave-induced fracturing should currently be regarded as a promising complementary stimulation technology rather than a mature replacement for conventional hydraulic fracturing.