Scaling Up the Non-Newtonian Flow Characteristics of Polymers, Foams, and Emulsions

Abstract

Abstract A generalized compositional thermal simulator is used to analyze the impact of the non-Newtonian flow characteristics of polymers, foams, and emulsions at three length/time scales. At the pore scale a novel use of a reservoir simulator is employed to create networks of varying topology in order to study the impact of porous media structure on rheological behavior. Aspects of non-Newtonian flow of polymers, foams, and emulsions at this scale are then compared and contrasted. In particular the suitability of viscometer power law parameters to porous media, and the role of pore constrictions in trapping and mobilization are considered. Subsequently, the non-Newtonian behavior of these fluids at the core and field scales are examined. It is shown that the impact of heterogeneity, crossflow and radial flow patterns, and region dependent trapping have analogies with the more microscopic scale. Furthermore, the shear rate dependence of in situ foam and emulsion generation suggests different modelling approaches at the core and field scales, with core scale rate processes replaced by pseudo-equilibrium K values at the field scale. Numerical aspects of non-Newtonian modelling (explicit versus implicit and block-centered versus face-centered velocity evaluation) are discussed briefly. Introduction One of the most intriguing aspects of enhanced oil recovery processes involving the flow of polymers, foams, and emulsions is their observed non-Newtonian flow behavior - the apparent viscosities of these fluids change with applied flow rates or shear. Although the underlying physical origin of this behavior is different for each type of fluid, two general questions can be applied in each case:What is the relationship between the rheological properties of these fluids as measured in a standard viscometer and their non-Newtonian behavior observed in a porous media at varioustime/length scales?What impact does this non-Newtonian behavior have on the recovery of oil with EOR methods? Both of these questions are addressed here using reservoir simulation. In presenting this unified simulation approach to polymer, foam and emulsion flow behavior, a useful concept is that of a "dispersed component": A dispersed component is defined as a semi-stable (non-equilibrium) dispersion of one phase transported in another continuous phase. For foams the dispersed component is a lamella, while for emulsions it is the droplet. Obviously, this definition blurs the traditional separation between components and phases. However, it has important practical consequences for modelling observed phenomena at any scale larger than the size of an individual dispersed component, as this report will demonstrate. CAPILLARY TUBE FLOWS OF DISPERSED COMPONENTS The non-Newtonian behavior of polymers, foam and emulsions are predominantly shear thinning, although the underlying physical mechanisms differ in each case. In addition, regions exist (high extensional flow/degradation/generation/coalescence) where this is not strictly true. P. 35^