Some insight into laboratory core floods using an NMRI technique

Abstract

Because of lack of knowledge concerning the fluid distribution in a core during flooding, most of the commonly utilised methods of interpreting dynamic displacement tests invoke the assumption of diffuse flow, core homogeneity and negligible capillary pressure gradient in the direction of flow. Such assumption may lead to gross error in interpreting relative permeability and also in translating laboratory core floods to the scale of numerical model grid cells (scale up). This work is aimed at trying to identify saturation profiles and gradients during a laboratory core flood utilising chemical shift imaging — a nuclear magnetic resonance imaging (NMRI) method. The preliminary results are rather interesting and suggest to us that capillary pressure gradient can be deduced from the core flood. This could allow separation between the viscous and capillary elements of fluid flow in a fractional flow equation and, in contrast to cases where capillary pressure is ignored, could lead to a different interpretation of relative permeability. The other matter that interests us is the possibility that separate identification of capillary and viscous force contributions may allow improved scale up criteria. In the present work, we describe elements of the laboratory investigation and the way in which results are used in a fractional flow equation. One-dimensional (1-D) imaging process is considered here, but it is capable of extension to 3-D by improved data logging methods and magnetic strength.