SYNCHROTRON-RADIATION MEASUREMENT OF MULTIPHASE FLUID SATURATIONS IN POROUS-MEDIA - EXPERIMENTAL-TECHNIQUE AND ERROR ANALYSIS

Multiphase flow in porous media is an important research topic. In sit u, nondestructive experimental methods for studying multiphase flow ar e important for improving our understanding and the theory. Rapid chan ges in fluid saturation, characteristic of immiscible displacement, ar e difficult to measure accurately using gamma rays due to practical re strictions on source strength. Our objective is to describe a synchrot ron radiation technique for rapid, nondestructive saturation measureme nts of multiple fluids in porous media, and to present a precision and accuracy analysis of the technique. Synchrotron radiation provides a high intensity, inherently collimated photon beam of tunable energy wh ich can yield accurate measurements of fluid saturation in just one se cond. Measurements were obtained with precision of +/-0.01 or better f or tetrachloroethylene (PCE) in a 2.5 cm thick glass-bead porous mediu m using a counting time of 1 s. The normal distribution was shown to p rovide acceptable confidence limits for PCE saturation changes. Source s of error include heat load on the monochromator, periodic movement o f the source beam, and errors in stepping-motor positioning system. Hy podermic needles pushed into the medium to inject PCE changed porosity in a region approximately +/-1 mm of the injection point. Improved ma ss balance between the known and measured PCE injection volumes was ob tained when appropriate corrections were applied to calibration values near the injection point. (C) 1998 Elsevier Science B.V.