LABORATORY INVESTIGATIONS OF IMMISCIBLE SAG DISPLACEMENT: THE EFFECTS OF SAG RATIO

Nitrogen is one of the gases used in the both miscible and immiscible gas injection processes into the reservoirs. There are some phenomena such asoverriding, fingering and channeling in heterogeneous formations can cause decreasing of break through time in production well during oildisplacement. Surfactant alternating gas injectionprocess is one of the methods commonly used to decrease this problem. The foam resulting from the contact of nitrogen and surfactant, causes increasing of injection gas viscosity. Consequently, the oil and gas contact time and sweep efficiency increases. Inthis paper, an experimental study of the effect of surfactant to gas ratio on oil recovery in secondary oil recovery process during execution of immisciblesurfactant alternating gas injection was examined experimentally. The experiments were performed with sand pack under certain temperature andpressure. However, before the experimental, the concentration of surfactant was optimized in order to minimization of its adsorption on rock surface. Then,the experiments were done with surfactant to gas ratio of 1:1, 1:2, 1:3, 2:1 and 3:1. Finally, the experimental results show that using theconcentration of 1500 ppm of surfactant solution can be used to perform the economic test. These resultsalso showed that the surfactant alternating gas ratioof 1:1 has the maximum oil removal efficiency and generating the foam in a porous media will increase the pressure of injection.