1. Gas properties, fundamental equations of state and phase relationships 2. Natural gas demand prediction: methods, time horizons, geographical scopes, sustainability issues, and scenarios 3. Machine Learning to Improve Natural Gas Reservoir Simulations 4. In situ stress and mechanical properties of unconventional gas reservoirs 5. Hydraulic fracturing of unconventional reservoirs aided by simulation technologies 6. Experimental methods in fracturing mechanics focused on minimizing their environmental footprint 7. Production decline curve analysis and reserves forecasting for conventional and unconventional gas reservoirs 8. Well Test Analysis for Characterizing Unconventional Gas Reservoirs 9. Carbon-Nanotube-Polymer Nanocomposites Enable Wellbore Cements to Better Inhibit Gas Migration and Enhance Sustainability of Natural Gas Reservoirs 10. Sustainability in Natural Gas Reservoir Drilling: A Review on Environmentally and Economically Friendly Fluids and Optimal Waste Management 11. Enhanced gas recovery technologies aimed at exploiting captured carbon dioxide 12. Sustainability Challenges for the Upstream Sectors of the Natural Gas Industry