Rapid fluid content measurement method for fingered flow in an oil–water–sand system using synchrotron X-rays

The complexity of simultaneous flow of water and non-aqueous phase liquids is largely unappreciated because few techniques permit accurate quantitative measurement of water and oil contents in rapidly changing flow fields. High intensity X-rays were used at the Cornell High Energy Synchrotron Source (CHESS) to obtain rapid, accurate, and non-destructive quantitative measurements of the changing fluid contents in a porous medium during infiltration events. Concomitant temporal pressure measurements were obtained for each liquid phase using rapidly responding tensiometers. The system was used for measuring temporal volumetric fluid content changes during a water finger infiltration into sand saturated with a NAPL (Soltrol-220) in a two-dimensional chamber. The fluid content distribution of a finger in the oil–water system was found to be similar to air–water systems. The hysteretic constitutive relationship between pressure and the content was developed from the data. The relationship was used to explain why the finger did not widen behind the tip, and why, upon re-infiltration, water followed the previously established path. These findings are relevant for cleanup of oil-contaminated sites because it aids in the understanding of hydrologic control which is an essential component of cost-effective in-situ remediation.