X ray and visible light transmission for laboratory measurement of two‐dimensional saturation fields in thin‐slab systems

Abstract

Two independent techniques, X ray absorption and light transmission, are developed and demonstrated for imaging transient saturation fields in thin‐slab porous systems. The techniques yield full two‐dimensional saturation fields with high spatial and temporal resolution. In the time required to make a single measurement by one of the traditional methods (e.g., gravimetric or gamma densitometry) an entire image consisting of hundreds of thousands of points is acquired by either the X ray or light technique. These methods are also very sensitive, capable of resolving a hundred or more levels of saturation at each of these points. Evaluation of these techniques is accomplished by direct comparison of X ray and light data as well as comparison with gravimetric and gamma densitometry data. Results of the comparison show very close agreement between the four techniques (on average within 5% saturation). These techniques represent useful tools for investigating processes governing unsaturated flow and transport through porous media.

Experimental Study on the Measurement of S-p Relations of LNAPL in a Porous Medium

“…In laboratory experiments, generally, the non-intrusive or non-destructive methods should be used to measure ‰uid saturation. Widely accepted in situ methods for measuring soil water saturation are radioactive methods such as the neutron scattering method (Gardner and Kirkham, 1951), X-ray or the gamma ray attenuation method (Host-Madsen and Jensen, 1992; Illangasekare et al, 1995aIllangasekare et al, , 1995b; Lenhard et al, 1993;Reginato and van Bavel, 1964;Tidwell and Glass, 1994), Time Domain Re‰ectometry (TDR) method (Topp et al, 1980), and so on. These methods are quite accurate and non-destructive; however, they require special caution to avoid possible health hazards or higher investment.…”

Probabilistic electrical resistivity tomography of a CO2 sequestration analog

“…A 12-bit CCD camera took images of the sand chamber with its focal plane 1.5 m away, yielding a pixel resolution of 0.2 mm × 0.2 mm. Saturation fields were calculated from grayscale pixel intensities using a well-established method proposed by Tidwell and Glass (1994) and further developed by Niemet and Selker (2001).…”

Multiphase Flow and Cavern Abandonment in Salt

“…Visualization was accomplished by means of light-transmission imaging (Tidwell and Glass, 1994). This involved placing the test cell in front of a computer stabilized bank of highintensity fluorescent light tubes.…”

“…Finally, each image is subtracted fiom the initially dry image to yield a two-dimensional map of the brine in the salt slabs. Because of the very low porosity of the salt we have not attempted to quantify the brine saturation in these images (see Tidwell and Glass, 1994); however, we plan to explore more quantitative imaging approaches in the future.…”