702 



Subsurface Geologic Methods 



ability of the rock to fluids. Research data available in the literature 



demonstrate that: 



(1) The permeability of a rock to the wetting-fluid phase de- 

 creases rapidly from unity at 100 percent saturation for small 

 decreases in the saturation of the wetting phase and correspond- 



liJ 

 O 



q: 



IxJ 

 Q- 



id 



+ 

 o 



100 



80 



60 



40 



20 







20 



40 



60 



80 



100 



So PER CENT 



Figure 378. Variation of relative permeability of unconsolidated sands to oil 

 and to water with oil saturation. K = 1.04 — 6.8 darcys. (After Leverett.) 



ingly for small increases in the saturation of the nonwetting 

 phase (fig. 378) . Moreover, the permeability to the wetting 

 phase decreases virtually to zero at a saturation of as great as 

 15 to 40 percent, depending upon the structure and composition 

 of the rock. Furthermore, the permeability to the wetting-fluid 

 phase is independent of the nature or number of nonwetting-fluid 

 phases. 



