Visualization experiments on polymer-weak gel profile control and displacement by NMR technique

The distribution and migration characteristics of weak gel in the core were observed by combining nuclear magnetic resonance (NMR) imaging technology with the core displacement experiment, and the oil displacement features of different polymer-weak gel combinations were examined with visualization experiments. Three combination patterns of polymer and weak gel were designed: waterflooding + polymer flooding (pattern 1), waterflooding + polymer flooding + weak gel flooding (pattern 2), and waterflooding + weak gel flooding + polymer flooding (pattern 3). The pressure variations, T2 spectra, nuclear magnetic resonance images, oil displacement efficiencies under the different patterns were analyzed. The results show that the nuclear magnetic images can not only provide the direct information of weak gel distribution and migration characteristics inside the core, but also reflect the distribution characteristics of remaining oil; the T2 spectrum characteristics indicate that both polymer and weak gel have the function of profile control and oil displacement, and the pattern 2 has the best profile control effect; of the three patterns, pattern 2 has the highest oil displacement efficiency of 78.84%, which is 18.33% higher than the displacement efficiency of water flooding in the initial stage.