Dynamic Monitoring of Polymer Flooding Using Magnetic Resonance Imaging Technology
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Applied Magnetic Resonance
ORIGINAL PAPER
Dynamic Monitoring of Polymer Flooding Using Magnetic Resonance Imaging Technology Hongxian Liu1 · Yao Ding2 · Weimin Wang2 · Yingkang Ma2 · Taotao Zhu2 · Deming Ma2 Received: 8 June 2020 / Revised: 9 September 2020 / Accepted: 30 September 2020 © Springer-Verlag GmbH Austria, part of Springer Nature 2020
Abstract 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 T 2 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 T 2 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.
Hongxian Liu and Yao Ding the authors have the same contribution. * Weimin Wang [email protected] 1
Faculty of Petroleum, China University of Petroleum–Beijing at Karamay, Karamay 834000, China
2
Department of Electronics, Peking University, Beijing 100871, China
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H. Liu et al.
1 Introduction Polymer flooding is an economical enhanced oil recovery method for heterogeneous reservoirs that is utilized after water flooding. It is generally accepted that the main recovery mechanism of polymers is to increase the water phase viscosity and decrease the water relative permeability due to polymer retention so that volumetric sweeps are improved by mobility reduction [1, 2]. In addition, the viscoelastic properties of polymers also have a certain role in improving the microscopic oil displacement efficiency [3–5]. Core flooding experiments are typically used to determine the optimal reservoir development option and to evaluate the effects of injected fluids that are specially designed to improve or enhance oil recovery [6, 7]. In conventional experiments, the core plug is generally regarded as a black box, and the bulk oil saturation and oil recovery
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