The Effects of Clay on the Displacement of Heavy Oil by Water

Abstract

Abstract The effects of clays on the displacement of heavy viscous oil by water are considered. Based on the assumption that the connate water is displaced ahead of the injected water in a waterflood, the theoretical flooding behaviour of homogeneous sands with small amounts of clay intermixed in the sands is investigated. Attention is given to the case where the relative permeability curve for the displaced connate water is higher than the relative permeability curve for the injected water. Under these conditions a simple graphical representation of the flooding behaviour is developed. Calculated results are presented which indicate that for highly viscous crudes displaced by fresh water the effects of small amounts of clays in the sands can cause large increases in the efficiency with which water displaces oil. Based on the calculated linear flooding behaviour a discussion is presented of the effects of clays on pattern waterfloods in which fresh water is injected. The report contains a considerable amount of evidence that indicates the effects of clays can cause large increases in the efficiency with which fresh water displaces oils with high viscosities. It is concluded that in spite of the difficulties encountered in injecting fresh water it may be a more desirable injection fluid than brine in some highly permeable reservoirs containing high viscosity crudes. The report also contains a review of the evidence of the effects of clays on core analyses and some speculations on the physical mechanisms by which clays affect the permeabilities of sands to water and oil.