Fractional Wettability Effects on Surfactant Flooding for Recovering Light Oil Using Teepol

Abstract The fractional or mixed wettability of porous media has been recognized as ubiquitous condition in the petroleum literatures. Fractional wettability refers to the fraction of the total pore surface area which is preferentially water or oil-wet. And this wetting condition of a reservoir rock plays a significant role in determining the oil recovery This paper presents laboratory analysis of the effect of wettability alteration on recovery mechanism and the effects of Teepol at different wettability conditions using a glass beads-pack. Oil wet condition was established by the use of kerosene and other fractional wettability conditions were also established. Six experiments were performed. In all the experiments, imbibition, drainage, water flooding, surfactant flooding and polymer flooding were carried out on the porous medium. 0.7PV surfactant solution (teepol) at a concentration of 0.9%wt and 1.1PV polymer solution (gum Arabic) at 5%wt concentration were used. In experiment A, B, C, D, E and Z (control), the porous medium was 100% water wet, 25% water wet and 75% oil wet, 50% water wet and 50% oil wet, 75% water wet and 25% oil wet, 100% oil wet, 100% water wet respectively. The results show that equal percent wettability of both water and oil and complete wettability of either oil or water yield more incremental oil when compared with those of 25% water wet and 75% oil wet condition and 75% water wet and 25% oil wet fractional wettability. Teepol is effective in lowering the oil-water IFT in all porous media with recovery ranging from about 75.5 to 90% of the residual oil saturation (ROS). Experiment C (50-50 fractional wettability) has the highest incremental oil recovery due to grain-to-grain interactive forces while experiment Z has the lowest recovery (about 41% of ROS). This strongly suggests mixed or fractional wettability reservoirs are good candidate of chemical EOR technique. However, even fractions contributions to the mixed wettability by both phases are required for optimum process performance.