Nikolay Evseev

Modeling of Pore-Scale Two-Phase Phenomena Using Density Functional Hydrodynamics

Predictive modeling of pore-scale multiphase flow is a powerful instrument that enhances understanding of recovery potential of subsurface formations. To endow a pore-scale modeling tool with predictive capabilities, one needs to be sure that this tool is capable, in the first place, of reproducing basic phenomena inherent in multiphase processes. In this paper, we overview numerical simulations performed by means of density functional hydrodynamics of several important multiphase flow mechanisms. In one of the reviewed cases, snap-off in free fluid, we demonstrate one-to-one comparison between numerical simulation and experiment. In another case, geometry-constrained snap-off, we show consistency of our modeling with theoretical criterion. In other more complex cases such as flow in pore doublets and simple system of pores, we demonstrate consistency of our modeling with published data and with existing understanding of the processes in question.

Multiphase flow modeling with density functional method

This paper is a review of applications of density functional theory (DFT) in compositional hydrodynamics. The basic idea is representation of the entropy or the Helmholtz energy of the mixture as the functional depending on the molar densities of chemical components (density functional). The hydrodynamics is governed by local conservation laws of chemical components, momentum, and energy, while constitutive relations and boundary conditions are introduced in accordance with the explicit form of the density functional. The general ideas and the history of the DFT in compositional hydrodynamics are discussed. Then the DFT for multiphase multicomponent mixtures is presented including the exposition of the first principles, governing equations and constitutive relations, and explicit expressions of density functional depending on physical situation. The DFT-based numerical simulator is described, and several multiphase simulation results are presented to illustrate the scope and effectiveness of DFT: sessile drop with and without surfactant, droplet breakup in shear flow, and three-phase hydrodynamics with mobile solid phase. Also, two practical scenarios with multiphase simulations in micro-CT porous rock models are presented: two-phase immiscible water-oil flow and three-phase water-gas-condensate flow with phase transitions. All numerical results are obtained by essentially the same code; both the number of chemical components and the Helmholtz energy have been set up in accordance with physical situation.

Modeling of surface phenomena in the presence of surface-active agents on the basis of the density-functional theory

Within the framework of the density-functionalmethod in multiphase multicomponent mixture hydrodynamics, the possibility of modeling surface-active agents on a “fluid-fluid” phase interface is shown. The method is based on the continuum description of multiphase mixtures with introducing terms quadratic in component density gradients to entropy or free energy. The determining equations are derived. Hydrodynamic model problems which demonstrate certain typical phenomena (the accumulation of surface-active agents on the phase interface, the corresponding decrease in surface tension, and the Gibbs and Marangoni effects) are solved numerically.

Modeling of nanoscale liquid mixture transport by density functional hydrodynamics

Modeling of multiphase compositional hydrodynamics at nanoscale is performed by means of density functional hydrodynamics (DFH). DFH is the method based on density functional theory and continuum mechanics. This method has been developed by the authors over 20 years and used for modeling in various multiphase hydrodynamic applications. In this paper, DFH was further extended to encompass phenomena inherent in liquids at nanoscale. The new DFH extension is based on the introduction of external potentials for chemical components. These potentials are localized in the vicinity of solid surfaces and take account of the van der Waals forces. A set of numerical examples, including disjoining pressure, film precursors, anomalous rheology, liquid in contact with heterogeneous surface, capillary condensation, and forward and reverse osmosis, is presented to demonstrate modeling capabilities.