Flow of dilute oil-in-water emulsions in porous media

The flow of dilute oil-in-water emulsions is of critical concern in produced water reinjection. Oil droplets and solids suspended in produced water are often hard to remove and are, therefore, reinjected into subsurface formations. A rapid injectivity decline in such water injection wells is commonly encountered.;This dissertation is aimed at investigating the mechanisms of permeability impairment caused by the flow of dilute oil-in-water emulsions in cores containing residual oil. The study has both experimental and modeling components.;The experimental program consisted of injecting well-characterized oil-in-water emulsions into cores containing a residual oil saturation. The permeability of different sections of the core as well as the droplet concentration and size distribution were measured as a function of time and position.;Experimental results indicated that the presence of residual oil had a profound effect on the measured permeability decline. Droplets were generated from the residual oil present at pore throats after a critical capillary number is exceeded. It was found that high injection rates and low permeabilities enhance droplet formation. The generation of droplets is a primary contributing factor to the permeability reduction observed in different sections in the core. The permeability of the core, the droplet concentrations, the concentration of emulsifier present, the flow rate, and the properties of the crude oil all play important roles in determining the extent and rate of permeability impairment.;Based on experimental data, a simplified mathematical model has been formulated to compute the permeability reduction and the droplet concentration in core flow tests. The model accounts for droplet trapping and generation phenomena. An empirical droplet-generation model is proposed based on the experimental observations. Reasonably good agreement is obtained between the model and the experimental results. The trends with flow rate and droplet concentration that are observed experimentally are also obtained from the model.;The study presented in this dissertation is the first systematic investigation of the flow of dilute oil-in-water emulsions in a porous medium with a residual oil saturation present. The results presented and their interpretation will provide new insights into the mechanisms responsible for injectivity decline in produced-water injection wells. The model proposed will form the basis of injectivity decline simulators for such water injection wells. (Abstract shortened by UMI.)...