Shale oil and gas show complex phase behavior variations with spatial and vertical heterogeneity. For example, Eagle Ford shale oil density decreases from northwest to southeast, and crude oil changes from black oil to volatile oil, gas condensate, and dry gas in turn. Due to different degrees of thermal evolution, crude oil composition changes with lithofacies and organic facies, and the oil density decreases vertically. From another point of view, many small pores in shale reservoirs may confine hydrocarbons' thermodynamic properties, reconditioning vapor-liquid equilibrium in porous media. Different approaches have been proposed to adjust thermodynamic properties to construct the crude oil phase envelope, but mature theory development is still ongoing.

Furthermore, Multiphysics models such as adsorption and diffusion complicate the fluid flow in porous media. Thermodynamics and kinetic studies relating to adsorption, diffusion, and convective flow in porous media need to be elaborated upon to strengthen our understanding of fluid flow in porous media.

The aim of this Special Issue is to investigate recent advancements in developing coupled fluid behavior in subsurface porous media. We aim to bring together original research and review papers highlighting recent progress in coupled theory and experiment studies and novel understandings of upscaling techniques from pore scale to core scale and reservoir scale. Pilot and field tests in unconventional shale oil and gas reservoirs as well as conventional reservoirs, considering the above multiphysics, like H2 generation and carbon storage, will also be welcome.

Potential topics include but are not limited to the following:

• Nanopore confinement thermodynamic model study
• Nanopore phase behavior experimental and simulation study
• Adsorptive gas flow in the shale porous media
• Filed investigations of reservoirs with mysterious production phenomena caused by complex flow and phase behavior
• CO2 and rich gas EOR studies in unconventional reservoirs focusing on the phase behavior coupled with flow
• Molecular simulation with insight into the flow kinetics with thermodynamics
• Diffusion simulations and experimental studies that occur between different phases with different compositions in unconventional reservoirs
• Upscaling studies of complex phase behavior and flow from pore scale to core scale and reservoir scale
• Coupled flow and phase behavior taking into geomechanics effect