Heavy oil-in-water emulsion flow and blocking mechanism in porous media

The application of heavy oil-in-water emulsion as a novel sealant in the near wellbore region is proposed in this research. The process in mind is one where a created emulsion will be injected, break and seal the porous matrix in the vicinity of the wellbore or at some pre-determined distance from it, thereby reducing water (and/or gas) coning or eliminating the leakage in abandoned wells. Laboratory experiments at micro- and macro-scale levels were performed to: (a) provide a detailed understanding of emulsion flow and blocking mechanisms and, (b) set criteria with which to control emulsion penetration depth before it breaks down and seals a porous medium.; In these experiments, well-characterized oil-in-water emulsions were injected into etched-glass micro-models and micro-models packed with glass beads. The effect of droplet-to-pore size ratio, droplet stability, oil and surfactant type and concentration were studied through visualization experiments. It was concluded that blockage occurred because of the size of the oil droplets was larger than the pore throat constrictions. The blockage was accelerated due to droplets coalescence as a result of a high shear rate or surfactant adsorption onto the porous medium. Furthermore, emulsion droplet size distribution, emulsion viscosity and oil droplets-to-water interfacial tensions increased as the surfactant content decreased, resulting in high capillary pressure across the trapped oil droplet.; The effects of oil type, rock permeability, injection velocity, and wettability alteration were also studied. The results indicated that a heavy oil-in-water emulsion sealed unconsolidated cores for long periods of time, and that emulsions carrying more viscous oils could resist higher pressures. Moreover, by conditioning the medium with surfactant and alkaline based pre-flush solutions, the emulsion penetration depth enhanced significantly. However, the emulsion may break down and emplace at a desired depth as a result of using low pH pre-flush solutions.; A novel sealant that uses a heavy oil-in-water emulsion to block the near wellbore matrix has been developed. Stable reduction in permeability to other fluids was observed as the plug withstood 42,500 kPa/m (about 1,800 psi/ft) pressure gradients. Criteria are defined for the field application of this blockage phenomenon.