704 



Subsurface Geologic Methods 



virtually becomes equal to the permeability obtained at 100 per- 

 cent saturation. Furthermore, the permeability to gas (a non- 

 wetting phase) is determined solely by the amount of gas pres- 

 ent — i.e., the gas saturation. However, the permeability to oil, 

 usually a nonwetting phase in sedimentary rocks, does depend 

 upon the distribution of other fluids, such as water and gas, and 

 therefore is not determined uniquely by the oil saturation alone. 



20 



30 40 50 60 70 



PERCENT LIQUID SATURATION 



80 



90 



100 



RELATIVE PERMEABILITY TO GAS AND OIL FOR WEST TEXAS DOLOMITES 



Wasson Field Doto (6) 



Sloughter Field Data 



Average of 26 cores from 3 West Texas 



Permion Dolomiles (6) 



Figure 380. Variation of relative permeability to oil and to gas of some dolomites. 



The mineral composition no doubt has some effect on the permeability- 

 saturation relationships exhibited by a particular rock — but less than 

 one would suspect — ^the general form of the relation being quite similar 

 in all respects for rocks as dissimilar as the Woodbine sand, the Big 

 Lake dolomite, and the San Andres dolomite (figs. 381, 382, and 383). 



