Potential of Spontaneous Emulsification Flooding for Enhancing Oil Recovery in High-Temperature and High-Salinity Oil Reservoir

Abstract

Emulsification tests and oil/water interfacial tension measurements were made to develop an alkali/surfactant spontaneous emulsification system to adapt the high-temperature and high-salinity in Shengtuo reservoir; also, oil displacement efficiency under different shear strength was investigated by a sandpack flood test. The results showed that the interfacial tension of oil/water could be lowered to an ultra-low level by a synergistic effect of alkali and surfactant, leading to spontaneous emulsification of oil in brine under condition of porous medium. When shear strength was low, the particle size of the formed emulsion droplet was larger, droplets might coalesce in the pore throat and generate a strong “Jamin” effect, and the mobility ratio of water to oil could be effectively reduced so as to increase the sweep efficiency and oil recovery. The particle size of the emulsion decreased with an increase of the shear strength, and emulsion droplets were insufficient to plug the water channel effectively and were entrained out of the formation with the displacing fluid due to the limited capability of reducing the water-to-oil mobility ratio, which resulted in lower oil displacement efficiency. Therefore, the entrapment of emulsion droplets was the main mechanism to enhance recovery, and oil recovery could be improved by reducing shear strength during flooding.

GRAPHICAL ABSTRACT

Keywords:

• Entrapment
• high temperature and high salinity
• mobility ratio of water to oil
• shear strength
• spontaneous emulsification
• sweep efficiency

Notes

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