308 



Subsurface Geologic Methods 



In general, the higher the permeability, the lower the connate-water satur- 

 ation. 



A large part of this section has been devoted to the determination and 

 discussion of connate-water saturation because it is considered the critical 

 key in data interpretation and the calculation of hydrocarbon reserves. 



Figure 131. Tabulated core data and interpretation for well C. The permeability 

 to dry gas is relatively high. Some samples showed a higher permeability 

 vertically than horizontally. In general the permeability distribution is good. 

 The residual-oil saturations are normal for water-free-oil production from this 

 sand. 



Core-Data Interpretation in Regard to Production 



The basic core data are of little value unless correctly interpreted 

 by qualified core analysts. By designating fluid contacts it is possible to 

 minimize completions in water sands. For example, if a six-inch perme- 

 able-water-sand zone is included in the completion interval, fluid from this 

 sand can drown as much as ten feet of gas or oil sand. Because of the 

 critical nature of completing oil wells with a gas cap or bottom water, it 

 is highly important that core depth and perforation or completion depths 

 agree. Many times the core analyst is held responsible for poor comple- 



