Optimization of Gravity-Stable Surfactant Flooding

Abstract

Abstract Horizontal surfactant floods are inherently unstable without mobility control. However, a vertical surfactant flood can be stabilized by gravity provided the velocity is below the critical velocity. A modified stability theory was validated by comparison with a series of surfactant displacement experiments. These experiments also demonstrate that the critical velocity can be increased by optimizing the viscosity of the microemulsion that forms when the surfactant solution mixes with the oil in the porous medium. The microemulsion viscosity is sensitive to formulation variables such as the amount and type of co-solvent added to the surfactant solution. By changing surfactant components, cosolvents, and the concentration of the co-solvents, we were able to successfully control the microemulsion viscosity at optimum salinity in order to optimize the critical velocities in each surfactant flood. The experiments using optimized microemulsions show that the surfactant flood velocity can be significantly inceased and still recover nearly 100% of the oil.