Multiphysics modeling of microwave heating-induced moisture and methane transport in shale gas reservoir

To advance shale gas extraction, this study investigates the potential of microwave irradiation, an auxiliary technique for hydraulic fracturing to exploit methane resources sustainably. A coupled multiphysics model with dual-porosity media theory is proposed to capture this complex evolution, considering the characteristics of two-phase flow within shale gas reservoirs. The model incorporates the interactions among electromagnetic effects, solid deformation, fluid and moisture transport, and heat transfer, which enables effective evaluation of the change of various reservoir parameters under microwave irradiation, along with the analysis of different factors' influences on water–gas transport properties and gas extraction efficiency. The findings indicate that relative humidity is crucial to water–gas flow dynamics, specifically, the increase in relative humidity enhances the contribution of adsorbed methane to cumulative methane production. Microwave heating considerably raises the water–gas exchange rate between matrix and fracture, and boosts shale gas' desorption efficiency during the later extraction stages. Improving reservoir permeability is a key to strengthening productivity; however, its impact on cumulative production becomes less significant beyond a threshold. Additionally, the decrease in the gas adsorption decay factor enhances cumulative production.