Micromodel study of two‐phase flow under transient conditions: Quantifying effects of specific interfacial area

Abstract

Recent computational studies of two-phase flow suggest that the role of fluid-fluid interfaces should be explicitly included in the capillarity equation as well as equations of motion of phases. The aim of this study has been to perform experiments where transient movement of interfaces can be monitored and to determine interfacial variables and quantities under transient conditions. We have performed two-phase flow experiments in a transparent micromodel. Specific interfacial area is defined, and calculated from experimental data, as the ratio of the total area of interfaces between two phases per unit volume of the porous medium. Recent studies have shown that all drainage and imbibition data points for capillary pressure, saturation, and specific interfacial area fall on a unique surface. But, up to now, almost all micromodel studies of two-phase flow have dealt with quasi-static or steady state flow conditions. Thus, only equilibrium properties have been studied. We present the first study of two-phase flow in an elongated PDMS micromodel under transient conditions with high temporal and spatial resolutions. We have established that different relationships between capillary pressure, saturation, and specific interfacial area are obtained under steady state and transient conditions. The difference between the surfaces depends on the capillary number. Furthermore, we use our experimental results to obtain average (macroscale) velocity of fluid-fluid interfaces and the rate of change of specific interfacial area as a function of time and space. Both terms depend on saturation nonlinearly but show a linear dependence on the rate of change of saturation. We also determine macroscale material coefficients that appear in the equation of motion of fluid-fluid interfaces. This is the first time that these parameters are determined experimentally.

Experimental study on nonmonotonicity of Capillary Desaturation Curves in a 2‐D pore network

“…In such cases, the dominance of viscous forces over capillary forces (high values of Ca) favors generation of large blobs by viscous fingering. By exceeding a threshold value of Ca, viscous forces of the invading fluid flowing alongside the blobs tend to mobilize or fragment the residual oil into small parts [ Ng and Payatakes , ; Chatzis and Morrow , ; Koplik and Lasseter , ; Dias and Payatakes , ; Hinkley et al ., ; Joekar‐Niasar and Hassanizadeh , 2012a, 2012b; Karadimitriou et al ., ] reducing the size of the trapped blobs as illustrated in Figure . These results are in good agreement with the stochastic simulation of the motion, breakup, and stranding of oil ganglia carried out by Ng and Payatakes [], which concluded that mobilized solitary ganglia are destined to either get stranded whole (intermediate values of Ca) or to break up in daughter small ganglia which subsequently get stranded (high values of Ca) [ Weinhardt and Heinemann , ].…”

Modeling of Horizontal Water Redistribution in an Unsaturated Soil

“…Projection of this surface onto the p c – S w plane would form the hysteresis loop of the primary (or main) drainage and imbibition curves. Several experimental and modeling studies have suggested that the saturation–capillary pressure interfacial area surface is indeed unique for all drainage and imbibition equilibrium points, whether on the main or on scanning curves (e.g., Held and Celia, 2001; Chen and Kibbey, 2006; Chen et al, 2007; Joekar‐Niasar et al, 2008; Joekar‐Niasar and Hassanizadeh, 2011, 2012; Karadimitriou et al, 2014).…”

Micro‐PIV measurements of multiphase flow of water and liquid CO2 in 2‐D heterogeneous porous micromodels

“…Simplified approaches that allow experimental visualization of the flow involve the use of so‐called micromodels. In these micromodels, idealized 2‐D porous media facilitate optical access and thus simultaneous observation of the flow in multiple phases [ Zhang et al ., ; Armstrong and Berg , ; Karadimitriou et al ., , among others]. More recently, a number of studies have reported measurements in such micromodels using advanced optical diagnostic techniques (e.g., micro‐PIV) to capture spatially and temporally resolved velocity data of immiscible multiphase flow [ Blois et al ., ; Kazemifar et al ., ; Kazemifar et al ., ; Roman et al ., ].…”