This paper shows the very low areal sweep efficiencies to be expected when water flooding in heterogeneous rock. In this study the permeability of the rock matrix was assigned different values to a 400 point grid comprising the flooding pattern. The entire matrix was composed of rock permeabilities distributed randomly between some range. When the lowest permeability was 0.1 md and the highest 100 md. the average sweep was found to be only 20 to 30 percent of the total area for a five-spot pattern. Many examples are given and charts are presented for estimating the areal sweep in flooding heterogeneous five-spot, staggered line-drive and direct line-drive patterns.
Surprisingly, the direct line-drive square pattern gives a higher sweep for very heterogeneous rock than the staggered line-drive or five-spot patterns.
Muskat presented the areal sweep efficiencies when flooding or cycling five-spot, direct line-drive and staggered line-drive patterns several decades ago.