Page 306 - Petrophysics 2E

LAB-DERIVED EVALUATION OF SHALY 277

Values of n* at different water saturations were calculated and
included in Table 4.13. The average saturation coefficient of the
core samples is obtained by dividing the sum of the individual
n* by the number of S,, points; thus, n* = (2.99 + 2.94 + - e +
2.77)/8 = 2.88.
Calculate 1; for several values of S, from:

and plot these points as shown in Figure 4.44. Table 4.13 is
a summary of these calculations.

Keelan and McGinley investigated the influence on calculated water
saturations when an average coefficient n* value for all cores is used
instead of using individual core n* values [32]. Figure 4.46 shows the
correlation of n and n* with porosity. Using the best-fit line for n*, new
n* points were selected for individual sample porosities and new water

Figure 4.46. Saturation exponent us. porosity for Shannon sand 1321.