This paper presents results that highlight some aspects not often considered when dealing with experimental relative permeability curves in heterogeneous media, a very common situation in natural sandstone samples.
When comparing curves obtained from the same core sample as a result of horizontal and vertical floodings, they show a large difference in residual oil values and in the general displacement performance. The information thus gathered indicates a systematic tendency towards notably lower residual oil in the case of vertical floodings.
These results are significant because of the large number of cases of vertical flooding occurring throughout the productive life of a reservoir, such as crossflow among strata of different permeabilities, predominantly segregate flow, expanding gas cap, flow from basal aquifers, etc. This is the reason for contesting the standard procedure of always using the same single set of relative permeability curves that, in practically all cases, are determined by horizontal flow.
Based on the results presented herein, it is suggested that the end points used in order to describe the different reservoir flow and production models be obtained using horizontal and vertical flooding, as well as by imbibition and capillary pressure tests.