| Although residual oil saturation has long been one of the most important criteria in reservoir engineering, little systematic research can be found in the literature. This dissertation is an attempt to supplement this weakness.;We have performed laboratory coreflooding experiments to investigate the effects of polymerflooding on residual oil saturation, as a function of heterogeneity, permeability, saturation history, polymer type, polymer slug size, and oil type. The cores were cut from Antolini rock samples, which was heterogeneous sandstone obtained from an Arizona outcrop. The Antolini rock samples were well stratified with high permeability contrast. The cores were characterized by air minipermeability measurements, which showed that the coefficient of variation was in the range of 0.6 and 1.2. The displacements in each coreflood included a first oilflood, a waterflood, a second oilflood, and a polymerflood. The waterflood and the polymerflood were performed at the same capillary number to eliminate the effects of capillary number on residual oil saturation. To investigate the effects of oil type, we used two types of oils in our experiments. To investigate the effects of polymer type, we used two types of polymers. To investigate the effects of polymer slug size, we used polymer slug injection in two of our experiments. To investigate the effects of initial condition, we used 0.1 pore volumes of water injection before polymerflood in one of our experiments.;On the contrary to the conventional wisdom that polymerflooding will not reduce residual oil saturation over waterflooding, our experimental results have shown that the polymerflooding did reduce the residual oil saturation to some degree, from 2 percent to 22 percent (of pore volume). The average reduction in residual oil saturation for the experiments was 6.6 percent. Our further analysis has revealed that the residual phase saturation was a strong function of permeability. The residual phase saturations were decreased linearly with the permeability. And the reduction in residual oil saturation by polymerflooding was increased linearly with the permeability.;This study was unique because there has been no other work found in the literature that is comparable to it. The results of this study can help provide guidance for the reservoir engineering to predict initial-residual oil phase saturations and the reduction in residual oil saturation by polymerflooding, both in computer simulation and in oil field development. |
