Residual oil saturation (calculated from the CMT images) versus treatment time for JF-2 MEOR (a) and biosurfactant MEOR (b). Data points at 0 h represent the average oil saturation value measured directly after water flooding from six replicate columns for each wettability tested. Data points at 84, 140, and 156 h represent the average oil saturation value measured at two separate locations in the same column during MEOR. Oil saturation error bars at 0 h (i.e., directly after water flooding) correspond to a confidence interval of 90%