Multi-molecular mixed polymer flooding for heavy oil recovery

Abstract

Polymer flooding has its superiority in heavy oil recovery due to the improvement of the mobility ratio of oil to the injected fluids. In this work, the multi-molecular mixed polymer flooding is proposed for heavy oil recovery. Firstly, the inaccessible pore volume and resistance coefficient are measured for the multi-molecular mixed polymer. The low-field nuclear magnetic (LFNMR) resonance technique is then applied to compare the performance of conventional polymer flooding and multi-molecular mixed polymer flooding for heavy oil extraction from the pore-scale perspective. Results show that the inaccessible pore of multi-molecular mixed polymer flooding is about 5.0% lower than the single molecular polymer flooding, of which the resistance coefficient is about 6.2 higher than the single molecular polymer flooding, indicating the potential of the multi-molecular mixed polymer flooding for enhancing heavy oil recovery. Moreover, the multi-molecular mixed polymer flooding shows excellent performance for heavy oil production compared to the conventional polymer flooding. Specifically, the total oil recovery for the multi-molecular mixed polymer flooding is measured about 4.2% higher than that of the conventional polymer flooding. In addition, based on the LFNMR scanning, the multi-molecular mixed polymer flooding is more efficient in extracting oil from the smaller pores. This study is expected to inspire new strategies for heavy oil recovery; more importantly, it may provide insights into the mechanism of polymer flooding for heavy oil extraction.