Page 61 - Standard Handbook Petroleum Natural Gas Engineering VOLUME2

Basic Principles, Definitions, and Data 49

Table 5-8
Values of Exponent in the Archie Equation for Clays

Mlmtral particle Shape factor exponent
Sodium montmorillonite 3.28
Calcium montmorillonite 2.70
Muscovite 2.46
Attapulgite 2.46
Illite 2.11
Kaolinite 1.87
From Reference 61

Table 5-9
Factors That Influence the m Exponent in Equation 5-49
for the Rock-Water Interface
1. Pore geometry.
a. Surface-area-to-volume ratio of the rock particle, angularity, sphericity.
b. Cementation.
c. Compaction.
d. Uniformity of mineral mixture.
2. Anisotropy.
3. Degree of electrical isolation by cementation.
4. The Occurrence of an open fracture.
From Reference 65.

Table 5-10
Factors That Influence the a Coefflclent in Equation 5-49
1. Surface conductance and ionic mobility occurring in water films adsorbed
to solid surfaces.
a. The cation exchange capacity of particular solid materials.
b. The quantity of water adsorbed to clay particles in the rock framework
or within the interstices.
2. Salinity of formation water.
3. Wettability relations between particular solid surfaces and hydrocarbons,
as they influence cation exchange.
4. The presence and distribution of electrically conductive solid minerals.
From Reference 65.

Rock Compressibility

The isothermal rock compressibility is defined as the change in volume of
the pore volume with respect to a change in pore pressure:
Cf = +( (5-63)

%)T