Page 359 - Reservoir Formation Damage

Inorganic Scaling and Geochemical Formation Damage 339

7. Calculation of mineral solubilities with and without accompanying
irreversible reaction,
8. Calculation of boiling, cooling, wall-rock alteration, ground-water
mixing with hot waters and evaporation, and
9. Equilibrium or partial equilibrium states in gas-solid-aqueous systems.
Plummer (1992)* states that forward geochemical modeling can be
used "in developing reaction models that can account for the observed
compositional-mineralogical relations in the deposit, if there are no
aqueous or solid data for the system."

Reaction-Transport Geochemical Modeling

The reaction-transport models describe the geochemical reactions under
the influence of fluid flow and convective and dispersive transport of
various species in geological porous media. These models couple the
geochemical reaction and the fluids and species transport submodels to
accomplish temporal and spatial prediction of the evolution of geo-
chemical reactions in compositionally-complex geological systems (Plummer,
1992). These models are more applicable in most petroleum reservoir
exploitation and scale formation studies.

Graphical Description of the
Rock-Fluid Chemical Equilibria

Properly designed charts provide convenient means of describing the
equilibrium chemical reactions of the rock-fluid systems. Frequently,
the pe - pH, activity-activity, and saturation index charts are facilitated for
convenient description of equilibrium chemical systems. The con-struction
of these charts are based on the description of chemical systems at thermo-
dynamic equilibrium. In this section, the theoretical bases, characteristics, and
utilization of these charts are described according to Schneider (1997).

Saturation Index or Mineral Stability Charts

Mineral stability charts are convenient means of representing the
various equilibrium reactions of the solid minerals and aqueous solutions
in geological porous media in terms of the saturation index concept.

* Reprinted from "Water-Rock Interaction," Proceedings of the 7th international symposium,
WRI-7, Park City, Utah, 13-18 July 1992 Kharaka, Y. K. & A. S. Maest (eds.), 90 5410
075 3, 1992, 25 cm, 1730 pp., 2 vols., EUR 209.00/US$246.00 GBP147. Please order
from: A. A. Balkema, Old Post Road, Brookfield, Vermont 05036 (telephone: 802-276-
3162; telefax: 802-276-3837; e-mail: info@ashgate.com).