Page 147 - Reservoir Formation Damage

Multi-Phase and Multi-Species Transport in Porous Media 129

sand, gels, paraffin, asphaltene, sulfur, precipitates, crystalline matter, mud
fines, debris, and bacteria; and (5) associates such as the pairs of ions and
molecules, coagulates of various particulates, micelles, and microemulsions.
The characteristics of the particulates play an important role in
formation damage. Based on their characteristics, particles can be clas-
sified as: (1) indigenous, in-situ generated, or externally introduced;
(2) dissolved or nondissolved; (3) water-wet, mixed-wet, or oil-wet;
(4) deformable (soft) or nondeformable (hard); (5) sticky or nonsticky;
(6) swelling or nonswelling; (7) organic or inorganic; (8) reactive or inert;
(9) biological or nonbiological; (10) growing or nongrowing; and (11) asso-
ciating or nonassociating.
The species content of a system can be expressed in a variety of
alternative ways:

1. mass concentration (all species)

_ mass of i
(7-1)
volume of mixture
2. molar concentration (preferred for dissolved species)

_ Cj _ mass concentration of i _ mole of i
(7-2)
molecular weight of i volume of mixture
M t
3. mass fraction (all species)

C; mass concentration of i mass of i
J
J
W.=-L = - — = - - - (7-3)
p density of mixture mass of mixture
4. mole fraction (preferred for dissolved species)
moles of i
x : = (7-4)
moles of mixture

5. volume fraction (preferred for particulates)
c
_ t _ mas $ concentration of i _ volume of i
(7-5)
p. density of i volume of mixture
6. volume ration (preferred for particulates)

_ volume of i
(7-6)
volume of k