The predictions of
the crystallization temperature and the amount
of precipitates of paraffin waxes at high pressure conditions may
be inaccurate using existing thermodynamic models. This is mainly
due to the lack of experimental data on the molar volume of solid
paraffins at high pressures. This inaccuracy is even more pronounced
for mixtures of high asymmetry. The present work provides a new accurate
modeling approach for solid–fluid equilibrium (SFE) at high
pressure conditions, more specifically, for highly asymmetric systems.
In contrast to the conventional methods for high pressure SFE modeling
which define a Poynting molar volume correction term to calculate
the paraffin solid phase nonideality at high pressures, the new method
exploits the values of thermophysical properties of importance in
SFE modeling (temperatures and enthalpies of fusion and solid–solid
transition) evaluated at the high pressure condition using a new insight
into the well-known Clausius–Clapeyron equation. These modified
parameters are then used for evaluation of the fugacity in the solid
phase at higher pressure using the fugacity of pure liquid at the
same pressure and applying the well-established formulation of the
Gibbs energy change during melting. Therefore, the devised approach
does not require a Poynting correction term. The devised approach
coupled with the well-tested UNIQUAC activity coefficient model is
used to describe the nonideality of the solid phase. For the fluid
phases, the fugacities are obtained with the SRK EoS with binary interaction
parameters calculated with a group contribution scheme. The model
is applied to highly asymmetric systems with SFE experimental data
over a wide range of pressures. It is first used to predict crystallization
temperature in binary systems at high pressures and then verified
by applying it on multicomponent mixtures resembling intermediate
oil and natural gas condensates.
In enhanced oil recovery terminology, dispersion refers to the mixing between two stationary or mobile miscible fluids brought together during miscible displacement, which is the result of many different mechanisms, such as molecular diffusion, Taylor effect, viscous fingering effect, and flow behavior around stagnant pockets. Dispersion process in reservoir rocks represents a combination of these mechanisms. In this article, the longitudinal dispersion coefficient is investigated using "Shan-Chen-type multicomponent multiphase lattice Boltzmann," which is a novel and easy way to implement and parallelize a method in computational fluid dynamics. It has shown that the lattice Boltzmann method is a promising approach with a potential capability for simulating fluid flows in different areas. In recent years, it has been used as a very powerful design tool in fluids engineering. The validity of this method is verified with an analytical solution of linear diffusion equation. The flow in fractures and porous medium is then modeled by this approach and the results show that lattice Boltzmann may provide a new route for simulation of miscible displacement.
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