Synchrotron X‐ray microtomography and interfacial partitioning tracer test measurements of NAPL‐water interfacial areas

Abstract

[1] Interfacial areas between an immiscible organic liquid (NAPL), and water were measured for two natural porous media using two methods, aqueous-phase interfacial partitioning tracer tests and synchrotron X-ray microtomography. The interfacial areas measured with the tracer tests were similar to previously reported values obtained with the method. The values were, however, significantly larger than those obtained from microtomography. Analysis of microtomography data collected before and after introduction of the interfacial tracer solution indicated that the surfactant tracer had minimal impact on fluid-phase configuration and interfacial areas under conditions associated with typical laboratory application. The disparity between the tracer test and microtomography values is attributed primarily to the inability of the microtomography method to resolve interfacial area associated with microscopic surface heterogeneity. This hypothesis is consistent with results recently reported for a comparison of microtomographic analysis and interfacial tracer tests conducted for an air-water system. The tracer test method provides a measure of effective, total (capillary and film) interfacial area, whereas microtomography can be used to determine separately both capillary-associated and film-associated interfacial areas. Both methods appear to provide useful information for given applications. A key to their effective use is recognizing the specific nature of the information provided by each, as well as associated limitations.

Comparison of interfacial partitioning tracer test and high‐resolution microtomography measurements of fluid‐fluid interfacial areas for an ideal porous medium

“…Analysis of the data sets indicated that REV requirements were met for image volumes of approximately 30–50 mm 3 (Figure 1). These results are similar to those reported in prior studies (Culligan et al, 2004; Brusseau et al, 2008). The volumes of the imaged zones were larger than the minimum for all data sets.…”

“…The results of prior studies have shown that interfacial areas measured with the IPTT method are larger than values measured with microtomography (Brusseau et al, 2006, 2007, 2008). The observed disparity has been hypothesized to result from the impact of porous-medium surface roughness.…”

“…As discussed by Brusseau et al (2008), fluid-fluid interfacial area in natural porous media is generally associated with both capillary and film domains. The capillary domain comprises interfaces associated with the bulk fluid (e.g.…”

Air-Water Interfacial Area and Capillary Pressure: Porous-Medium Texture Effects and an Empirical Function

“…It is critical to note that areas obtained with this method represent total areas, in that both capillary-associated and film-associated interfacial areas are included in the measurements. In addition, they incorporate interfacial area associated with microscopic surface roughness [Brusseau et al, 2006, 2007, 2008]. It is useful when comparing data for multiple porous media to normalize the measured A ia values by the specific solid surface area (s) measured using a method such as N 2 /BET.…”

Characterization of nanoparticle transport through quartz and dolomite gravels by magnetic resonance imaging

“…While providing more spatial detail on NP transport, the 2D transport profile must still be inferred from the ten detector points (much of the column is still unseen). Gamma radiation and X-ray micortomography have been used for porous media characterization (Illangasekare et al 1995), fluid distribution (Brusseau et al 2008) and solute-fluid transport (Hofstee et al 1998) experiments. A major shortcoming of this method is at a single location; it requires relatively large counting times, leading to total counting times of several hours to produce an image (Werth et al 2010).…”