Analysis of the literature (Refs. 70-103 in Ref. 13) suggests no reason to believe that emulsions have any placement or permeability-reduction advantages over gelants and gels.13 For concentrated emulsions (either oil-in-water or water-in-oil), their behavior in porous media can be described using standard relative-permeability concepts.92-93 Therefore, the placement properties of concentrated emulsions are similar to those of viscous gelants.18 Also, the literature indicates that concentrated emulsions provide very low permeability-reduction values (residual resistance factors less than 1.5).13,92,93 Furthermore, residual resistance factors provided by concentrated emulsions do not increase with increasing initial rock permeability.92,93
Dilute emulsions show behavior that can be described by a modified deep-bed filtration theory.94-96 Ref. 13 contains a detailed examination of the literature and models that describe the flow of dilute emulsions through porous media. We can summarize the results of this analysis as follows: although several features of emulsion flow through porous media remain unanswered, our analysis of the literature indicates that emulsions or emulsion/gel combinations will not perform significantly better than gels as blocking agents, particularly in the areas of placement characteristics and permeability-reduction properties. Our calculations indicate that at best, the placement properties of emulsions will approach those for a low-viscosity gelant.