Page 53 - Reservoir Formation Damage
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Mineralogy and Mineral Sensitivity of Petroleum-Bearing Formations 37
5
Figure 2-24. Correlation of volume change vs.water pickup during swelling
(after Civan, ©1999 SPE; reprinted by permission of the Society of Petro-
leum Engineers).
(2-24)
where § is porosity, t is time, S is the rate of water absorbed per unit
bulk volume of porous medium.
Civan (1996) developed an improved equation assuming that the rate
of porosity variation by swelling is proportional to the rate of water ab-
sorption and the difference between the instantaneous and the terminal
or saturation porosities:
(2-25)
subject to
(2-26)
Integrating Eqs. 2-25 and 26 yields:
In (2-27)
from which the porosity variation by swelling can be expressed by:
