The development of unconventional gas/oil reservoirs has attracted a lot of attention across the academic and industry communities, particularly for shale gas/oil reservoirs, as well as coalbed methane (CBM), both of which possess abundant nanoscale pores. In addition, in compliance with the current knowledge, their exploitation complexity stems from the existence of nanoscale pores, leading to a great discrepancy in terms of fluid occurrence and flow behavior. From the microscopic viewpoint, fluid-solid interactions will gradually become prominent in affecting nanoconfined flow behavior, while it can be neglected for the pores in conventional reservoirs (micrometers or even larger).

To date, although massive research efforts have been performed to shed light on the nanoconfined behavior, some critical issues that are required to be further addressed remain unclear. For example, shale and low-rank coal reservoirs possess dual-wettability properties, while the wettability-induced control effect on the nanoconfined gas-water behaviors is still vague. Meanwhile, the unique properties, such as viscosity, critical parameters, and interfacial tension of the fluid at the nanoscale, are needed to be revisited and characterized accurately, as reported by a great deal of experimental and simulation evidence. Hydraulic fracturing is a commonly utilized approach to improve formation permeability, while microscopic investigation of fracturing fluid invasion or flowback process is still lacking. Accordingly, the successful development of unconventional reservoirs requires a clear understanding of nanoconfined fluid behavior, entailing additional in-depth investigations on the basis of previous contributions.

To bridge the knowledge gap, this Special Issue is dedicated to attracting high quality original research and reviews, focusing on the nanoconfined fluid occurrence and flow behaviors.

Potential topics include but are not limited to the following:

• Nanoconfined fluid chemical and physical properties (viscosity, surface tension, wettability, etc.)
• Adsorption/desorption of oil, gas, and water in unconventional rocks
• Phase behavior in unconventional rocks
• The nanoscale phenomenon occurred in CO2 geological sequestration and enhanced oil recovery (EOR) process
• Single/multiphase transport within nanoporous media
• Characterization and reconstruction of unconventional rocks
• Novel method or technology to enhance nanoconfined flow capacity
• Simulation methods (LBM, PNM, MD, etc.) for modeling fluid behaviors in unconventional rocks
• Novel experimental and numerical modeling methods for fluid transport in unconventional porous media
• Evaluation of macroscopic parameters of unconventional rock (permeability, relative permeability, capillary, etc.)
• Machine learning and data-driven science applications for the microscopic phenomenon in unconventional reservoirs
• Upscaling methods of nanoscale dynamical process