The exploitation of unconventional oil/gas reservoirs (such as shale oil/gas, tight oil/gas, natural gas hydrate (NGH), coalbed methane (CBM), oil shale, etc.), which have been proved with considerable resource reserves, can provide plentiful fuel. CO2 fracturing and replacing these unconventional oil/gas from low-permeable subsurface formations with abundant nano-/micro-pores has been proposed as one of the promising approaches of enhanced oil/gas recovery with geologically sequestrating CO2. The oil/gas release and CO2 sequestration in these unconventional reservoirs involves complex flow and transport in a hierarchical network of nanopores, cracks, and microfractures (such as adsorption/desorption in shale and coal seams, formation/decomposition of hydrates, replacement by CO2, thermal cracking of oil shale, etc).

The traditional theory and technology for conventional reservoirs may be not appropriate for these unconventional oil/gas reservoirs. New knowledge and understandings of multiphase and transport of CO2-oil-natural gas in these subsurface formations are urgently needed to guide the development of unconventional oil/gas reservoirs, and the related theory, experiment and simulation studies are rapidly developing.

This Special Issue focuses on the multiphase flow and transport of CO2 in subsurface unconventional oil/gas reservoirs. We aim to bring together original research and review articles highlighting the recent advances of new techniques, the latest understanding of the underlying mechanisms, advanced algorithms for modeling, innovative methods of experiments, field pilots, etc. on CO2 geological storage and enhanced oil/gas recovery in unconventional reservoirs. Other studies on CO2 geological storage and exploitation of unconventional subsurface energy (such as geothermal, dry hot rock) are also welcomed. We invite researchers in the aforementioned fields to contribute with submissions.

Potential topics include but are not limited to the following:

• CO2 geological storage with enhanced oil/gas recovery gas/liquid flow and transport in the fracture matrix system of porous media
• Adsorption/desorption mechanism of gas in shale, coal seams, and so on
• Replacement mechanism of shale gas, natural gas hydrate, CBM, etc. by CO2
• Kinetics of CO2/CH4 hydrate formation/decomposition
• Microfluidics related to the unconventional oil/gas and CO2 geological storage
• CO2 geological storage with enhance geothermal system
• Exploitation technologies (such as fracturing) of unconventional oil/gas reservoirs
• Other experiments, simulations and field tests related to the exploitation of conventional/unconventional reservoirs