Phase field modelling of spinodal decomposition in the oil/water/asphaltene system

Abstract

In this paper the quantitative applicability of van der Sman/van der Graaf type Ginzburg-Landau theories of surfactant assisted phase separation [van der Sman et al., Rheol. Acta, 2006, 46, 3] is studied for real systems displaying high surfactant concentrations at the liquid-liquid interface. The model is applied for the water/heptane/asphaltene system (a model of heavy crude oil), for which recent molecular dynamics (MD) simulations provide microscopic data needed to calibrate the theory. A list of general requirements is set up first, which is then followed by analytical calculations of the equilibrium properties of the system, such as the equilibrium liquid densities, the adsorption isotherm and the interfacial tension. Based on the results of these calculations, the model parameters are then determined numerically, yielding a reasonable reproduction of the MD density profiles. The results of time-dependent simulations addressing the dynamical behaviour of the system will also be presented. It will be shown that the competition between the diffusion and hydrodynamic time scales can lead to the formation of an emulsion. We also address the main difficulties and limitations of the theory regarding quantitative modelling of surfactant assisted liquid phase separation.

Phase-field theory of multicomponent incompressible Cahn-Hilliard liquids

“…For instance, surfactant controlled nanoshell formation opened a new chapter in targeted drug delivery [33]. Another crucial field is energy: a controlled emulsion → emulsion transition in the CO 2 /water/heavy crude oil system would result in an efficient and environmentally sound combination of CO 2 storage and Enhanced Oil Recovery [34,35].…”

“…The system of dynamic equations described by (35), (42) and (47) are solved numerically on a fully periodic 2dimensional domain by using an operator-splitting based quasi-spectral semi-implicit time stepping scheme [32] combined with the spectral Chorin's projection method as follows. The dynamic equations can be re-written in the form…”

A lattice boltzmann approach to surfactant‐laden emulsions

“…A similar approach was used by Van der Sman and Van der Graaf to show Ward‐Tordai like kinetics of surfactant adsorption. This method was further developed by Tóth and Kvamme to show slowed down phase segregation due to the presence of surfactants, and applied to oil, water, and asphaltene systems . A thorough review of models for ionic surfactants has been presented by van der Sman and Meinders, which also gives model taxonomy, distinguishing between Eulerian and Lagrangian approaches, with the various ways of simulating surfactants with different degrees of complexity that have been developed so far.…”

Phase-field modeling of isothermal quasi-incompressible multicomponent liquids

“…Although the theory of multicomponent liquid diffusion is well developed and in use in chemical engineering and materials science [1][2][3][4], the generalization of theory describing the time evolution of liquid systems being out of mechanical equilibrium is still lacking. Nevertheless, even results of simple continuum theories indicate that the hydrodynamic mode might influence pattern formation significantly even on small length scales [5][6][7][8], which indeed comes into play in microfluidics [9][10][11][12], or even in oil industry related research: CO 2 /water/hydrocarbon emulsions may offer a novel and ultimate solution for the global CO 2 storage problem with combined Enhanced Oil Recovery, however, the continuum description of kinetic processes in these molecularly complex liquids is nontrivial [7]. Besides, significant volume changes occur in case of formation/dissociation of CO 2 /CH 4 hydrates (clathrates), also necessitating thus a hydrodynamic description.…”