A New Technique for Visualizing the Distribution of Oil, Water, and Quartz Grains in a Transparent, Three-Dimensional, Porous Medium

Abstract

Summary A new technique for visualizing the distribution and structure of oil, water, and quartz particles in a transparent, three-dimensional (3D), porous medium is presented. A laser light sheet illuminates a slice of a rectangular cell containing a mixture of oil, water, and quartz particles. All three phases have the same refractive index. The quartz particles. All three phases have the same refractive index. The quartz particles do not fluoresce. From the different fluorescence colors of particles do not fluoresce. From the different fluorescence colors of water and oil, the cross-sectional distribution of the three phases can be visualized. Photographs of different cross sections are presented that show both the solid grain structure and trapped oil blobs. This technique can be used to study two-phase flow in porous media. Introduction Several different methods have been used to study various aspects of flows in porous media. We will review some methods for the study of saturation distribution, viscous fingering, and blob-size distribution. We will then describe a new method that can be used for these studies. Electrical resistivity and nuclear magnetic resonance (NMR) have been used to measure the average saturation in core. X-ray, gamma-ray, neutron beam, microwave, very-high-frequency oscillator, and NMR imaging techniques have been used to monitor saturation profiles alone the length of a porous medium. A photometric method has also been used for 3D, transparent porous media. These methods give an average saturation over a length scale much larger than the characteristic size of a pore. This average saturation information is valuable for some purposes but is inadequate for pore-size scale phenomena, which are the ingredients of the overall results. For example, in EOR it is important to know not only the magnitude of the residual oil saturation, but also how the oil is distributed inside the interstices of the rock before the best method for mobilizing the residual oil can be determined. Viscous fingering in porous media has been studied with 3D, transparent porous media, fluorescence photographic techniques, and X-ray tomographic techniques. In transparent-flow models, only a thin layer of particles can be used because recording and quantifying the results in three dimensions is difficult. In the fluorescence photographic technique, a water-soluble dye that adsorbs photographic technique, a water-soluble dye that adsorbs on solid surfaces is used. The porous medium has to be cut to visualize and to photograph the distribution of water and oil in the cross section under ultraviolet lighting. The experiment cannot be continued once the core is cut. The X-ray tomographic technique is limited by its resolution of about 800 m. Other methods are needed to study the residual-oil-blob structure. Blob-size distribution has been studied with etched patterns on transparent glass plates and polymerization of nonwetting phase in water-wet rocks. The latter method involves the dissolving of the rock after the model oil phase is solidified through polymerization at the conclusion of each coreflooding experiment. Then, the sizes of the solidified oil blobs are analyzed. A major drawback of this method is that the experiment cannot be continued once the core is dissolved. The shrinkage of the oil blobs during polymerization and breakage in the process of dissolving the core and separation of these blobs from the rock debris can also affect the results. In this paper, we describe a new technique for the study of two-phase flow in transparent porous media. Although only artificial porous media can be used, this technique shows directly the cross-sectional distribution of the three phases inside a 3D medium. phases inside a 3D medium. Experiments and Results A schematic of the experimental setup is shown in Fig. A 5145- [514.5-nm] argon-ion laser beam of 400-mW power is transformed into a laser sheet by a beam expander and then a cylindrical lens. This laser sheet illuminates a slice of a rectangular cell containing two immiscible liquids and transparent quartz particles of the same refractive index. The quartz particles do not fluoresce, but the two liquids fluoresce in different colors in the presence of the laser light. The cell is mounted on a micrometer stage so that different cross sections can be illuminated by the beam. The distribution of the three phases at different cross sections of the porous medium phases at different cross sections of the porous medium is recorded by a camera through a laser filter. SPEFE P. 205