In this paper, main
and interactive effects of four important factors,
temperatures, adsorption thicknesses, fracture apertures, and feed
CO2 concentrations, on the thermodynamic phase behavior
for CO2 storage processes in the fractured nanopores of
shale/tight reservoirs with adsorptions are investigated. First, a
modified analytical equation of state is developed by considering
the effects of confinements and intermolecular interactions, which
is applied to predict the confined pure/mixing fluid phase behavior
in fractured nanopores coupled with a novel empirical correlation
for the adsorption thickness and the fracture geometry equation. Second,
the aforementioned four important factors are studied to evaluate
their main and interactive effects on the phase behavior of pure CO2, N2, O2, Ar, alkanes of C1–10, and their mixtures. It is found that all the pure and mixing fluid
pressures monotonically and linearly increase to different extents
with an increasing temperature. Moreover, the pressures/critical shifts
and critical properties perform downward and upward parabola curves
with respect to the adsorption thicknesses, respectively. On the other
hand, the pressures/critical shifts are monotonically decreased, while
the critical properties increase with the fracture apertures increasing
from 0.01 up to 10 nm and remain constant afterward. By increasing
the feed CO2 concentrations, the critical shifts and pressures
for all of pure and mixing fluids are increased, while both the critical
pressures and temperatures decrease. In addition, three interactive
effects on the phase behavior are analyzed that the effect of a single
factor behaves differently with the variations of any other factors. Finally, the amounts of
the N2, O2, Ar, and light alkanes of C1–4 are suggested to be controlled for CO2 storage in the
fractured nanopores because additions of these components strongly
affect the mixture phase behavior.