In recent years, unconventional oil and gas reservoirs have attracted great attention due to their unique properties. Compared to conventional reservoirs, these unconventional systems have low permeability (including a large number of nanopores) and consist of inter-particle pore networks with very poor connectivity. The fractured system constitutes a hierarchical network of nanopores, cracks, and micro-fractures, which form multiscale fracture network-pore dual media. Its complex microstructures make it difficult to characterize the flow of oil and gas flow by traditional approaches. Therefore, new multiscale and multiphysics methods are being continuously developed to characterize low permeability and fractured reservoirs. This helps describe flow and transport mechanisms.

The aim of this Special Issue is to bring together original research articles and review articles highlighting recent advances in various subjects addressing new multiscale and multiphysics approaches to fluid flow in porous media, especially for unconventional oil and gas systems. We invite investigators to contribute with submissions that will explore the many aspects of modelling and characterization in low permeability and fractured reservoirs.

Potential topics include but are not limited to the following:

• Multiphase flow in unconventional reservoirs
• Multiscale and multiphysics modelling in unconventional reservoirs
• Fracture characterization and hydraulic fracturing in unconventional reservoirs
• Enrichment and migration mechanisms in nanopores
• Pore-scale modelling in unconventional reservoirs
• Scale and capillary effects in unconventional reservoirs
• Gas adsorption and desorption in unconventional reservoirs
• Interface and surface effects in unconventional reservoirs
• Petrophysical properties in unconventional reservoirs