Quantifying Pore Scale Distribution of Light, Medium, and Heavy Crude Oil Fractions in a Homogeneous Porous Medium

J. Ghosh and G. R. Tick
Department of Geological Sciences, University of Alabama, Tuscaloosa, Alabama

Crude oil mobility is highly dependent on the pore geometry, acting capillary forces, and the interfacial tension between the oil, water, and solid phases in porous media. This research aims to understand how specific oil fraction affects oil mobilization and to determine the dominant processes controlling oil recovery during surfactant flooding at the pore scale. Elucidating such mechanisms influencing oil mobilization can help improve techniques for enhanced recovery from existing reservoirs. A pore-scale study was conducted to characterize various fractions of crude oil morphology and their distribution in homogeneous porous medium. Multiple columns packed with natural accusand to establish desired porosity domains were injected with three fractions of crude oil. Moreover, the columns were flooded with anionic surfactant to study the temporal changes in oil distribution. Synchrotron X-ray microtomography was used to obtain high resolution 3-D images of the two-phase crude oil/water system before and after surfactant flooding events. Preliminary results show that the light crude oil exhibited more complex heterogeneous distributions before and after surfactant flooding when compared to the medium fraction crude oil distributions. However, in comparison to the light fraction crude oil, 95% of the medium fraction oil distribution was significantly smaller in terms of total blobs/ganglia size and comprised significantly greater numbers of blobs/ganglia (20 times more oil blobs/ganglia) within the same homogeneous system. The initial results indicate that specific oil fraction is an important factor controlling blob morphology and overall crude oil distribution which has significant implications on oil recovery. Further study on this research will not only be helpful in determining the primary variables controlling the oil blob entrapment and recovery but also help in understanding the utility of synchrotron X-ray microtomography for quantifying crude oil distribution at pore scale level.

AAPG Search and Discover Article #90087 © 2008 AAPG/SEG Student Expo, Houston, Texas