Quantifying Light, Medium, and Heavy Crude Oil Distribution in Homogeneous Porous Media

Crude oil recovery is highly dependent upon the physical heterogeneity of media and resulting distribution of the oil-phase within the pore spaces. Factors such as capillary force, the geometry of the pore spaces, and interfacial tension between the oil blobs and water-wet porous media will ultimately control the recovery process. Pore scale studies were conducted to study the distribution and the morphology of various fractions of crude oil in increasingly heterogeneous porous media. In addition, experiments were also carried out to characterize the temporal changes in distribution and morphology of the oil phase after a series of surfactant flooding events. Specifically, columns were packed with three different porous media with increasing heterogeneity and distributed with three different fractions (light, medium, and heavy) of crude oil. The columns were imaged using synchrotron X-ray microtomography before and after a series of surfactant floods to quantify the resulting crude oil distributions over time. Preliminary results show that the light crude oil was more heterogeneously distributed than the medium fraction crude oil within the same porous media type both before and throughout the series of surfactant floods. It was also observed that approximately 95% of the medium fraction crude oil blob-size distribution was smaller (<0.0008 cu mm) than that of the light crude oil, encompassing a significant number of blob singlets. The lighter crude oil fraction has the median blob diameter approximately 20 times greater than that of the medium crude oil fraction. These results further reveal that that oil extraction and recovery is highly dependent upon the oil fraction, the presence of small- sized blob singlets, and the resulting distributions present within porous media before and during surfactant flooding. This research will not only be helpful in understanding the factors controlling crude oil mobilization at the pore scale but also test the utility of synchrotron X-ray microtomography to quantify pore scale distribution at high resolution.