High Resolution Characterization of Crude Oil Distribution in Porous Media Using Synchrotron X-Ray Microtomography

With the growing demand of petroleum, and inadequate supply throughout the world it is essential to develop improved techniques for enhanced recovery of crude oil from reservoirs considered economically infeasible for recovery. A better understanding of the crude oil distribution and reservoir heterogeneity on mobilization at the pore scale can help in formulating techniques for more effective oil recovery. Crude oil migration is a function of interfacial tension and the capillary forces existing between the oil/water/rock interfaces. This research integrates the use of surfactant flushing techniques and high resolution imaging to better understand the processes controlling the enhanced recovery of the oil trapped within pore networks. Synchrotron X-ray microtomography was used to obtain high resolution 3-D images (9.2 micron image resolution) of a two-phase oil-water system. A series of water-saturated columns packed with both homogeneous and heterogeneous sand were injected with three different fractions (light, medium and heavy) of crude oils. The columns were flushed with an anionic surfactant to induce enhanced mobilization of the oil trapped within the pore spaces. A series of images were taken prior to and during surfactant flushing. The surfactant-induced flushing experiments resulted in various oil recovery efficiencies depending on porous medium and oil fraction. The outcome of this research demonstrates the utility of synchrotron X-ray microtomography for characterizing the morphology, distribution, and evolution of oil (e.g., oil/water/solid interfacial area, capillary forces, etc.) within various porous media under enhanced-mobilization surfactant flushing. These high resolution imaging techniques can provide invaluable insight for evaluating the pore-scale processes controlling recovery of oil.