INJECTION OF DISPERSED OIL-IN-WATER EMULSION TO IMPROVE VOLUMETRIC SWEEP EFFICIENCY DURING WATER FLOODING OF OIL RESERVOIRS

During water flooding of heterogeneous oil reservoirs, early breakthrough of water can occur and lead to poor volumetric sweep efficiency. Macro-emulsions with oil droplets dispersed in a continuous water phase [oil-in-water (o/w) emulsions], have the potential to block high-permeability zones in these reservoirs, and thereby improve the volumetric sweep by diverting the water flow from high-permeability layers toward lower-permeability layers. In the present work, the potential for produced water with dispersed oil to block sandstone rocks (with permeability of 150-2000 mD) was investigated. Different o/w emulsions with similar oil concentrations as in the produced water were prepared using synthetic oil and crude oil. Water-soluble surfactant was dissolved in synthetic formation water and homogenized with oil using a high-shear rate mixer at different speeds and mixing times. The prepared emulsions were injected into sandstone cores. A Coulter Counter Multisizer was used to measure the droplet size distributions in the injected emulsions and the produced effluent. The droplet size distributions in the emulsions and the pore throat size distributions in rock were compared. The flooding experiments demonstrated that injection of emulsions can significantly reduce the permeability, and depending on the initial permeability of the rock the permeability reduction was up to 47%. Emulsion has the potential to accelerate and improve oil production and reduce the water cut at low-cost investment. Further work is required to qualify this method for field applications.