Page 505 - Petrophysics

MULTIPLE-PERMEABILITY ROCKS 473

TABLE 7.3
CORE DATA FROM AN OIL WELL

Depth, ft Permeability, mD Flow Capacity, mD-ft
6,204-6,205 105 105
6,205-6,206 150 150
6,206-6,207 132.5 132.5
6,207-6,208 95 95
482.5

Figure 7.15. Radial jlow in parallel beds.

that the properties of a core will change. This is from slightly to very
considerably once the core is brought to the surface, due essentially
to the drop in pressure from thousands of psia in the reservoir to 14.7 psia
at the surface. The range of this change is dependent on the lithology of
the reservoir rock (sandstone, limestone, etc.), degree of consolidation
and fracturing, etc. Table 7.3 is obtained by recording permeability values
vs. depth from Figure 7.15.

The average permeability in the 6,204-6,208 ft segment is 482.5/4 =
120.5 mD. Using Equation 7.151 for the entire core, one obtains:

27
k.h-
CJI- - 1,886 mD - ft
i= 1

and the average permeability is equal to:

k = 1,886/27 = 70 mD