Evidence of New Instability Thresholds in Miscible Displacements in Porous Media

Abstract

We study the stability of the downdip displacement in a porous medium of a dense and viscous fluid by a lighter and less viscous fluid, and vice versa. Conventional predictions based on a Long-Wave (LW) theory lead to identical instability thresholds for the two flows. A Short-Wave (SW) analysis suggests that instability sets in earlier than the LW predictions and that the two thresholds are different in the two flows. Using an acoustic technique in 3D displacements, we have determined these thresholds and the instability diagram. Our data support the SW approach.