Unconventional gas (including shale and coal gas) is causing a shift in the dynamics of the international energy structure. Successfully addressing the impact of different fluids (e.g., CH₄ and other hydrocarbons, CO₂, and water) on flow behaviours in unconventional gas reservoirs is still a serious scientific spotlight and challenge. Because of the complex mechanism of gas, fluid, and/or solid flow behaviours in the shale/coal gas exploitation, multidisciplines are involved, including geoscience, rock mechanics, multicomponent and multiphase flow, geochemistry, and thermodynamics.

Therefore, this special issue is focusing on the impact of different fluids (e.g., CH₄, CO₂, and water) on flow behaviours and on gas extraction. This special issue accepts high quality articles containing original research results of multiphase flow and/or multiphysics coupling theories, simulations, experiments, and technologies for coal/shale gas exploitation. The accepted papers will show a diversity of new developments in these areas.

Potential topics include but are not limited to the following:

• Physical behaviour of natural gas flow in shale or coal
• Multiphase flow mechanics in shale or coal
• Gas-water-rock interactions in shale gas or coal
• The role of fluids in enhanced gas recovery
• Hydraulic fracturing mechanics of gas shale or coal
• Geomechanics of shale gas or coal seam gas extraction
• Impact of temperature on gas-rock interactions in gas shale or coal