STEAM COREFLOODS WITH CONCURRENT X-RAY CT IMAGING

A series of steam corefloods has been performed utilizing X-ray CT imaging to monitor phase saturations during the floods. A numerical simulator was used to analyze the experimental results. The steamfloods of initially water-filled sandpacks were carried out at low enough flow rates that capillary pressure was comparable in magnitude with viscous pressure drop. Numerically matching the observed pressure drops provided a significant test of the assumed steam-water capillary relationship. A capillary pressure curve of Leverett j-function form was found suitable for the simulations. The steam relative permeability curve was found by numerically matching both pressure drop and CT saturation data. The expected steam frontal behaviour was seen in the CT images, but the images also revealed unexpectedly large variations in water saturation transverse to the steam propagation direction. Although core porosity derived from the CT images showed no significant variation across the core, it was hypothesized that small variations in steam-water capillary pressure could have resulted from more subtle core packing variations. The expected type of core heterogeneity was subsequently confirmed by subjecting the core to petrographic image analysis. Numerical simulations embodying a realistic degree of core heterogeneity were able to reproduce the transverse saturation variations as a consequence of capillary crossflow.