312 



Subsurface Geologic Methods 



Edwards limestone in Caldwell and Guadalupe Counties in south Texas 

 often show as much as 45 percent residual-oil saturation. Where oil pro- 

 ductive, this limestone averages 20 percent in total-water saturation. 

 As discussed elsewhere in this paper, it is assumed by core analysts in that 

 area that the total water is the connate-water saturation. Porosity char- 



Figure 132. Gas- and water-permeability relationships for well C. These data em- 

 phasize the importance of making water-permeability tests. The sand would 

 favorably respond to gas injection. Some portions of the sand would respond 

 to salt-water injection, but fresh water will cause swelling of the hydratable 

 materials in the sand, and restriction of flow rates will result. 



