Description: This paper describes a series of experiments that used X-ray tomography to visualize the mobilization of remaining oil by Alkaline Surfactant Polymer (ASP) flooding after conventional waterflooding. The experiments were conducted in cores drilled from Bentheim sandstone outcrop material with diameters of approximately 7.55 cm and lengths of 14.9, 27.5 and 100 cm. The crude used in the experiments has an in-situ viscosity of about 100 cP and contains petroleum acids that are converted to soaps in the presence of alkali. Application: In addition to pressure and effluent data collected during conventional coreflood experiments phase and saturation distributions in space and time are needed to more completely interpret the results of core floods. This additional information reveals underlying mechanisms, and assists the development of models that capture the physics of ASP that can ultimately be used to provide field scale predictions for ASP performance. Results, Observations, and Conclusions: • A significant oil bank was created, propagated, and produced in each of the experiments. • The size of the oil bank in terms of length and maximum oil saturation is largely dependent on the post-waterflood saturation distribution along the cores. • Large variations in both the absolute value and the spatial distribution of the post-waterflood saturation distribution were observed in the different experiments. • A characteristic self-similar cross-sectional averaged oil saturation profile develops for floods conducted in the longer length cores. • Detailed analyses of individual frames revealed separate “oil” and “ASP fingers” in the area downstream of the oil bank. Significance: The displacement mechanisms involved in ASP flooding relatively viscous crudes are revealed by X-ray CT visualization. The resulting improved understanding of the process increases the confidence in the potential full-field application of ASP flooding.


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