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178 Reservoir Formation Damage

(9-43)

where k° is the high-temperature (T —> °°) limit of the rate constant.
The effects of various conditions on dissolution rates, including litho-
logic variation, hydrodynamics, ionic strength, saturation state, mixed-
kinetic control, and surface treatment, have been investigated by Raines and
Dewers (1997, 1997), Hajash Jr. et al. (1998), and Merino and Dewers (1998).

Crystal Surface Displacement by Dissolution
and Precipation

The dissolution and precipitation of a crystalline matter in contact with
a solution can be studied by measuring the progress of the crystal surface
as a function of time. Hunkeler and Bohni (1981) and Dunn et al. (1999)
used this technique. Civan (2000) determined that the position of the
progressing crystal surface could be correlated by:

r
-"»,\ _ •
In -kM (9-44)
JC-Jt,
for which x, x 0 and x t are the instantaneous, initial, and final surface
positions, respectively, k is a rate constant, and M is the amount of solute
precipitated or dissolved, given by:

(9-45)

where t is time, c 0 and c, are the solute concentrations of the solution at
the beginning and equilibrium, respectively, and D is the diffusion
coefficient of the solute. Civan (2000) verified this model using the Dunn
et al. (1999) measurements of the pit depth during barite dissolution.

References

Arshad, A., & Harwell, J. H., "Enhanced Oil Recovery by Surfactant-
Enhanced Volumetric Sweep Efficiency," SPE 14291, Annual Technical
Conference and Exhibition of SPE, Las Vegas, Nevada, September 22-
25, 1985.
Atkinson, G., & Mecik, M., "The Chemistry of Scale Prediction," J. of
Petroleum Science and Engineering, Vol. 17, No. 1/2, February 1997,
pp. 113-121.