A multi-scale experimental study of hydrophobically-modified polyacrylamide flood and surfactant-polymer flood on enhanced heavy oil recovery

Abstract

A large amount of residual oil remained in heavy oil reservoirs after water flood due to its viscosity nature. And it has been validated that chemical flood, if applied appropriately, is an efficient and economical EOR method for deeply buried or thin heavy oil reservoirs. A multi-scale experimental evaluation workflow was designed to explore the mechanisms behind the production of residual oil in heavy oil reservoirs by chemical flood. And we conducted three multi-scale experiments to evaluate the performance of hydrophobically-modified polyacrylamide (HMHPAM) flood, surfactant-polymer (SP) flood and their combination. Based on the results of corefloods and medical CT scans, we demonstrated the EOR potential of HMHPAM flood (HPF) synergy with SP flood (SPF). After each coreflood, two samples were drilled from the heterogenous core used in the macro-scale experiment. And the micro-CT scan results of these samples visualized the distribution of oil phase and aqueous phase in each coreflood at the pore scale, and further quantified the decrease of continuous oil clusters caused by the HMHPAM solution and following injected fluids. Besides, we also observed the linear relationship between the volume of each oil cluster against its surface area and the logarithmic relationship between the volume of discontinuous oil cluster and its cumulative contribution to total oil volume. Moreover, a simple method to calculate the oil-water proportion in pores was developed to correlate the relationship between the displacement efficiency of each pore and its pore size. Results showed that the relationship between oil saturation in each pore and its pore size followed the power law correlation. Moreover, the pore-scale analysis also validated that the residual oil in most pores after water flood was effectively mobilized by the synergy of HPF and SPF.