One-dimensional saturation distribution (saturation profile) and subsequently the saturation gradients in core floods were obtained directly from measurements using nuclear magnetic resonance (NMR) imaging. The core floods (water displacing oil in a water-wet Portland limestone core plug) were conducted at a very low flood rate, hence the saturation profile was influenced by the contribution of both viscous and capillary forces. The imbibition capillary pressure curve for the limestone rock was available and was used in conjunction with the measured saturation profile to quantify the capillary pressure gradients. This paper reports a successful approach to conducting and interpreting laboratory displacement tests at viscous-capillary force ratios typical of oil reservoirs.
This test demonstrated the NMR imaging technique as a useful complementary tool for laboratory study of water -oil displacement in cores. The practical contribution of this work is that it demonstrates the possibility of analysing laboratory core flood tests which yield information on both viscous and capillary forces, and hence the potential for scaling-up relative permeability data from laboratory tests to simulator-scale grid blocks using displacement force ratios.