Plugging Ability of Oil-in-Water Emulsions in Porous Media: Experimental and Modeling Study

[Graphics] Emulsion flow behavior in porous media is predominantly affected by the emulsions droplet size distribution, as the macro flow character is determined by the micro transport phenomena of emulsion droplets passing through pore constrictions. In this work, oil-in-water emulsions (O/W) with different droplet sizes but with the same oil concentration were first prepared and characterized by their interfacial tension, size distribution, stability, and bulk viscosity. Sandpack flow tests were then conducted to quantitatively investigate the plugging characteristics of the different emulsions in porous media. The results show that pressure drop of the emulsions in 1 mu m(2) permeability sandpacks initially increases as emulsion droplet size increases from 1.57 to 3.58 mu m, but then begins to decrease as the droplet size continues to increase. For a single emulsion droplet, a larger droplet size can result in a greater capillary resistance force, as it has a more significant "Jamin" effect in pore constrictions. However, for an emulsion system, the total pressure drop is also affected by droplet number. A larger droplet size means a smaller droplet number in the emulsion system. The macro flow character of emulsions in porous media is determined both by droplet size and droplet number. A new mathematical model, which incorporates geometry of the porous media, emulsion droplet size, emulsion droplet number, and interactions between droplets and porous media was developed to theoretically describe the plugging of an emulsion in the sandpacks. For the first time, this model takes into account the size difference between the pore body and the pore throat of a real porous medium when simulating emulsion transport. Results calculated from the newly proposed model appear to match well with the experimental data, with the smallest average error being 7.67%.