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56 Reservoir Formation Damage

Figure 3-4. Description of the pore volume attributes (after Civan, ©1994;
reprinted by permission of the U.S. Department of Energy).

number varies in the range of 6 < Z < 14 (Sharma and Yortsos, 1987). For
cubic packing, Z = 6 and <J> = 1 - n/6. The coordination number can be
determined by nitrogen sorption measurements (Liu and Seaton, 1994).

Pore and Pore Throat Size Distributions

Typical measured pore body and pore throat sizes, given by Ehrlich and
Davies (1989) are shown in Figure 3-7. Figure 3-8 shows the pore throat
size distribution measured by Al-Mahtot and Mason (1996). The mathematical
representation of the distribution of the pore body and pore throat sizes in
natural porous media can be accomplished by various statistical means. The
three of the frequently used approaches are the following:

1. Log-Normal Distribution (not representative)
2. Bi-Model Distribution (fine and course fractions)
3. Fractal Distribution

Log-Normal Distribution. Because of is simplicity, the log-normal
distribution function given below has been used by many, including Ohen
and Civan (1991):

2
F(D) = (2^ JD)- 1/2 expj-|[ln(D/Z) m)/^] j, 0 <£><<*> (3-16)