Theoretical Aspects of Emulsification in Porous Media

Abstract

Abstract A theoretical analysis of the mechanism of emulsification in porous media is presented. As an initial step in the investigation of the dispersion of one liquid in another, the hydrodynamic stability of a liquid layer surrounded by two other liquids is studied by the application of perturbation methods. Criteria for the hydrodynamic stability of the liquid layer are developed and the critical condition at which the instability occurs is predicted. Any disturbance of the interface is amplified, and, finally, jets of one liquid shoot out into the other phase. The radius of the droplets, as well as the phase. The radius of the droplets, as well as the number of droplets, formed are then determined. The analysis presented pays due care to the viscometric aspects of the dispersion of one fluid into another. The mechanism oil emulsification proposed is based on the hypothesis that viscosity proposed is based on the hypothesis that viscosity differences between displaced and displacing liquids can lead to emulsion formation. Introduction A considerable amount of the world's crude oil is produced in the form of stable emulsions. These produced in the form of stable emulsions. These must be broken down into their two constituents, crude oil and brine, before sale and transportation of the former and disposal of the latter. The application of new recovery methods such as thermal simulation and surfactant flooding has, in many cases, accentuated the problem of emulsion formation. This, together with the introduction of new recovery methods using emulsions or emulsion floods, has led to considerable interest in both the generation and the flow of emulsions. Since there is sound evidence that emulsions are generated in some instances while liquids are flowing in porous media, we have investigated some of the viscometric aspects of emulsification by considering the hydrodynamic stability of liquid-liquid interfaces in porous media. porous media. GENERAL CONSIDERATIONS Research on emulsification of liquids can be divided in two broad categories the physical processes involved in the production of an emulsion processes involved in the production of an emulsion in the form of fine droplets of one liquid in another, and the physicochemical aspects of the stabilization of these droplets. These aspects have been reviewed in detail in two monographs and more recently by Raghavan. The literature to date has focused its attention principally on the stabilization aspect because it is a "slow" process and thus can be studied in greater detail. The disruption of bulk liquid to form droplets is more difficult to study because it is a "fast" process and, consequently, it has received very little attention. In a fast process dynamic properties should play a greater process dynamic properties should play a greater role than equilibrium characteristics. For example, the theoretical calculation of energy requirements for emulsification falls far short of those actually found by experiment if only equilibrium properties, such as concentration of emulsifier, surface energy, etc., are considered. Inclusion of dynamic quantities such as viscosity of fluids and velocity result in experimental results and theoretical calculations being in closer agreement. This together with other studies has demonstrated the need for studying the initial disruption of the bulk fluids in dynamic terms rather than under conditions of equilibrium. It has been suggested by Rajagopal that a profitable method of investigating emulsion generation profitable method of investigating emulsion generation is through the study of the hydrodynamic stability of certain flow motions. Several types of unstable flow are well documented. The most common one is the transition from a laminar to a turbulent flow regime, wherein the viscous forces which keep small disturbances in check are overwhelmed by the inertial forces. The Kelvin - Helmholtz instability results due to the differential tangential velocities of two inviscid fluids and the interface may become unstable at even very small velocities. SPEJ P. 153