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Digitale Medien

Computer Modeling for Geothermal Systems: Predicting Carbonate and Silica Scale Formation, CO2 Breakout and H2S Exchange (1998)

MØller, Nancy ; Greenberg, Jerry P. ; Weare, John H.

Springer

Transport in porous media 33 (1998), S. 173-204

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ISSN: 1573-1634

Schlagwort(e): chemical models ; simulations ; calcite ; solubility ; carbon dioxide ; geothermal ; carbonate ; hydrogen sulfide ; thermodynamic.

Quelle: Springer Online Journal Archives 1860-2000

Thema: Geologie und Paläontologie , Technik allgemein

Notizen: Abstract This paper describes chemical equilibrium models for predicting carbonate and silica scale formation, CO2 breakout and H2S gas exchange in geothermal brine systems to high concentration and temperature. The equilibrium description is based on a minimization of the free energy of the system with solute activities described by the semiempirical equations of Pitzer (1973; 1987). The carbonate model is parameterized by appropriate osmotic, electromotive force and solubility data (T ≤ 250°C) available in binary and ternary solutions in the seawater Na–K–H–Ca–Cl–SO4–H2O system. The silica model is parameterized by solubility data to 320°C in the Na–Mg–Cl–SO4–SiO2–H2O system. The H2S model is parameterized by solubility data in the H2S–NaCl–H2O system to 320°C. The predictive capabilities of the models are demonstrated by comparison to both laboratory and field data. Examples have been given to illustrate the use of the carbonate model to predict downhole brine compositions in contact with specified formation minerals, temperature and pressure effects on carbonate scaling, the effect of scale inhibitors and breakout characteristics. Application of the silica model demonstrates the effect of temperature on silica scale formation. These illustrations show that the models can be used to reliably predict important chemical behavior in geothermal operations.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1023/A:1006501927827

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Digitale Medien

Discontinuous approximate molecular electronic wave-functionsBased on a thesis submitted by E. W. Stuebing to the Johns Hopkins University in partial fulfillment of the requirements for the degree of Doctor of Philosophy, 1970. Aided by a research grant to The Johns Hopkins University from the National Science Foundation. (1977)

Stuebing, Edward W. ; Weare, John H. ; Parr, Robert G.

New York, NY : Wiley-Blackwell

International Journal of Quantum Chemistry 11 (1977), S. 81-102

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ISSN: 0020-7608

Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: Following Kohn (reference 4), Schlosser and Marcus (reference 3), and Weare and Parr (reference 2), an energy functional is defined for a molecular problem which is stationary in the neighborhood of the exact solution and permits the use of trial functions that are discontinuous. The functional differs from the functional of the standard Rayleigh-Ritz method in the replacement of the usual kinetic energy operators T̂(μ) with operators T̂′(μ) = T̂(μ) + Î(μ), where Î(μ) generates contributions from surfaces of nonsmooth behavior. If one uses the ∇Ψ · ∇Ψ way of writing the usual kinetic energy contributions, one must add surface integrals of the product of the average of ∇Ψ and the change of ∇Ψ across surfaces of discontinuity.

Zusätzliches Material: 5 Ill.