Tight/shale gas, oil reservoirs and heavy oil reservoirs are referred to as typical unconventional reservoirs, which have held worldwide attention in terms of energy sustainable development. Chemical properties of underground fluids and rocks under relative high pressure and temperature are of critical importance to determine flow characterization in gas and oil reservoirs, such as fluid phase behavior, interfacial tension, and chemical interaction between rocks and fluids.

However, the flow mechanisms are not understood clearly from the perspective of chemistry during enhancing oil and gas recovery from unconventional reservoirs. Thermal methods used in heavy oil development, hydraulic fracturing in tight/shale reservoirs, and CO2 enhanced oil and gas recovery processes make the underground fluid-rock system more complex. Therefore, understanding the chemical properties and mechanisms is especially important in unconventional oil and gas reservoirs.

This Special Issue aims to attract the recent advances on novel findings of flow mechanisms and experimental/simulation methods to enhance oil and gas recovery in unconventional reservoirs, based on the chemistry of the underground fluid-rock system. It welcomes related high-quality research papers as well as review articles that summarize the current state of the art in such areas.

Potential topics include but are not limited to the following:

• Pore-scale studies of enhanced oil and gas recovery mechanisms considering chemical properties, such as wettability, phase behavior, and interfacial tension
• Adsorption/Desorption in shale reservoirs
• Hydraulic fracturing fluid formula and formation damage issues
• New enhanced oil and gas recovery theories, methods, and experiments during CO2 flooding
• Physicochemical phenomenon in the process of chemical and gas flooding and various synergistic methods to improve unconventional gas and oil recovery