Magnetic resonance studies of core flooding for enhanced oil recovery

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University of New Brunswick


Magnetic resonance (MR) and magnetic resonance imaging (MRI) were employed to study oil and water behaviors during core flooding for enhanced oil recovery (EOR). A recently developed k-t accelerated Spin Echo Single Point Imaging (k-t SE-SPI) method was employed to determine the one-dimensional (1D) water saturation distribution and spatially resolved T₂ distribution during waterflooding and polymer flooding in homogeneous Berea core plugs. The T₂ lifetime reveals pore scale fluid behaviors. k-t SE-SPI significantly improves measurement sensitivity and image quality compared to the conventional SE-SPI method. A high-speed three-dimensional (3D) MRI technique, π[pi]Echo Planar Imaging (π[pi]-EPI), was employed to monitor oil displacement. High quality 3D oil saturation images were acquired, revealing different oil distribution patterns in homogenous and heterogeneous porous media. Fluid quantification with π[pi]-EPI measurements was consistent with conventional MR/MRI measurements. A newly developed MR/MRI compatible metal core holder was employed to monitor core flooding processes at representative reservoir conditions. The new core holder is based on a high strength Hastelloy alloy, permitting MR/MRI measurements at 5000 psi and temperatures above 100 °C. Two EOR methods, polymer flooding and low salinity waterflooding (LSF) were studied with MR/MRI methodologies. The influences of rock wettability and oil properties on polymer flooding for EOR were examined. In situ oil saturation profiles during waterflooding and polymer flooding were determined from the MRI measurements. The pore scale oil behaviors were evaluated with bulk T₂ measurements. A novel concept, T₂ Logarithmic Mean Ratio (TLMR), is proposed to observe T₂ trends during flooding processes while minimizing the influence of the rock matrix and the nature of the fluids. SE-SPI MRI measurements were employed to determine the oil saturations and spatially resolved T₂ distributions at several LSF stages. A differential relaxation time distribution method is proposed to estimate the oil and water saturation. A kaolinite-coated sand pack was prepared as a model porous media for LSF.