Miscellaneous Subsurface Methods 



703 



(2) The permeability of a rock to the nonwetting-fluid phase 

 (figs. 378, 379, 380, 381, 382, and 383) has a real, consistent, 

 and experimentally reproducible value greater than zero only 

 after its saturation has increased from zero to a minimum value 

 of from 5 to 20 percent, depending upon the structure and com- 



.0 



0.8 



0.6 



o» 



o 

 o 



0.4 



0.2 



0.0 







20 40 60 



Sro PER CENT 



80 



100 



Figure 379. Variation of relative permeability of sands to oil and to gas with 

 oil saturation. 1 — Consolidated sands; 2 — unconsolidated sands. 



position of the rock. Thereafter, as the saturation to the non- 

 wetting phase increases slowly at first and then more and more 

 rapidly until at a saturation of from 60 to 90 percent, the exact 

 percentage depending on the structure and composition of the 

 rock, the permeability to the non-wetting phase (figs. 378, 379) 



