Some Experiments on the Flow of Miscible Fluids of Unequal Density Through Porous Media

Abstract

Introduction Craig, et al investigated the effect of gravity on frontal displacements for circumstances in which the gravity forces were significant. Blackwell, et al, dealt with the other extreme in which gravity forces were negligible. The considerable difference between their results is illustrated in Fig. 1 where the breakthrough recoveries are plotted against the mobility ratio. The experiments described in the present paper were conducted to examine how the transition from the one extreme case to the other occurs when the gravity forces are gradually reduced.The transition is well illustrated by the production history after breakthrough. Fig. 2 shows how the number of pore volumes which must be injected at a constant rate to displace 98 per cent of the original fluid depends on the gravity force. For each mobility ratio there is a transition range, and a very significant change in the number of pore volumes occurs when this range is transversed. This range of the gravity force is physically linked withtheformationofviscousfingers.A single finger is predominant for larger gravity forces; a multiplicity of fingers is formed for smaller gravity forces. Improved recovery and the occurrence of multiple fingers is concomitant with a large increase in the amount by which the fluids are mixed within the porous medium.The transition range depends on all the dimensionless groups which characterize the problem; but this dependence has not been exhaustively studied as yet and only fragmentary results are discussed in this paper. SPEJ P. 277^