Polymer flooding is a vital method for the enhanced oil recovery of heterogeneous formations after water flooding. However, few visualization approaches are available to conduct the online monitoring and the non-invasive evaluation of polymer flooding experiments in natural rock cores. In this study, online dynamic magnetic resonance imaging (MRI) and T₂ distribution measurements were employed to monitor polymer flooding in a natural layered core using low-field MRI equipment. A modified spin echo (SE) imaging technique featuring half Fourier acquisition and a short echo time (3.5 ms) was used to achieve dynamic MRI images during flooding with a temporal resolution of 93 s. Moreover, online T₂ distribution measurements by the Carr-Purcell-Meiboom-Gill (CPMG) pulse sequence were utilized to estimate the bulk remaining oil saturation to validate the MRI results. Furthermore, the spatial distribution of the displacement efficiency was obtained through MRI signal processing and was visualized via a pseudo-colour mapping technique. A statistical analysis was carried out to estimate the change in the mean of the spatial distribution of the displacement efficiency. The results show that an improvement in the oil recovery from the natural layered core by polymer flooding after water flooding can be intuitively observed by the proposed method. Our low-field MRI methods provide quantitative and revealing information that can be beneficial for flooding mechanism studies of enhanced oil recovery.

聚合物驱是注水后提高非均质地层采收率的重要方法。但是，很少有可视化方法可用于对天然岩心中的聚合物驱油实验进行在线监控和非侵入性评估。在这项研究中，在线动态磁共振成像（MRI）和T ₂分布测量被用于使用低场MRI设备监测天然分层岩心中的聚合物驱。改进的自旋回波（SE）成像技术具有一半的傅立叶采集和较短的回波时间（3.5 ms），用于在洪水期间以93 s的时间分辨率获得动态MRI图像。而且，在线T ₂利用Carr-Purcell-Meiboom-Gill（CPMG）脉冲序列进行的分布测量可估算剩余的大部分油饱和度，以验证MRI结果。此外，通过MRI信号处理获得了位移效率的空间分布，并通过伪彩色映射技术将其可视化。进行统计分析以估计位移效率的空间分布平均值的变化。结果表明，所提出的方法可以直观地观察到注水后通过聚合物驱从天然层状岩心中采收率的提高。我们的低场MRI方法可提供定量和揭示性信息，这些信息可能有助于提高采油率的驱油机理研究。