SATURATION GRADIENTS IN DRAINAGE OF POROUS-MEDIA - NMR IMAGING MEASUREMENTS

A steady-state method recently proposed for measuring two-phase flow p roperties of a porous medium is supplemented by NMR imaging for measur ing the saturation gradients which are allowed to persist in the speci men. The method relies on a strong capillary end effect which is assum ed to be enforced by an outlet capillary pressure boundary condition, but direct verification of this has not hitherto been available. For c onstant flow rates, incremented stepwise, steady-state profiles of hyd rocarbon saturation S(o) are obtained which agree with predictions tha t they be monotonic, nonintersecting, and convex. Using D2O for the aq ueous phase allows unambiguous detection of hydrocarbon by NMR, and im aging measurements of transverse relaxation time T2 were included in t he protocol. T2 shows a dependence on S(o) which is mild but not negli gible for quantitative NMR imaging.