| dc.description.abstract | In this work, a modified workflow for incorporating molecular effects into a macroscopic
fluid flow model via a mesoscopic transition model to more uniformly ascertain transport
properties during pore scale analysis, is presented and validated. A combined lattice
Boltzmann-molecular dynamics (LBMD) simulation approach to address this issue is employed.
The hydrocarbon and shale system taken under consideration here were modeled
in molecular form as n-octane and silica respectively. The n-octane was set up using the
united atom (UA) model. The interaction forcefields primarily employed for the MD system
included the standard Lennard-Jones potential, the transferable potentials for phase
equilibria (TRAPPE) and the Buckingham potential. The properties studied here were
the volumetric flux per unit area, apparent permeability and general fluid dynamics for
hydrocarbon flow in the system.
Results from the MD showed a non-linear relationship between the force and the noctane
density. This force was then incorporated into the LB system which already had
a Peng-Robinson equation of state embedded into a fluid-fluid particle interaction forcing
function. With the variation of the Knudsen number which accounts for slip effect (or
gradual deviation from continuum), the fluid dynamics of the system was then modeled.
Analysis showed that the slip effect as a function of the Knudsen regime was non-linearly
proportional to the volumetric flux per unit area, and thus the deduced permeability of
the fluid. The LBMD prediction of apparent permeability showed good agreement with
established apparent permeability correlations for shale found in literature. Good qualitative
agreement with flow dynamics was also achieved when compared to lab-on-a-chip
experiment, representative of nanoscopic shale media and with all results obtained without
parameter fitting.
This work aims to extend current understanding of fluid flow behaviour below the
continuum regime and improve the accuracy of apparent permeability computation on
tight rock geometric imagery, typical of shale rock physics when producing hydrocarbons
from shale gas reservoirs. This will be fundamental in the development of a more robust
and complex pore-scale modeling framework for simulating more accurate subsurface flow
dynamics. | en |
