The prediction of mineral solubilities in natural waters: A chemical equilibrium model for the NaKCaMgClSO4H2O system at temperatures below 25°C

Spencer, Ronald J.; Møller, Nancy; Weare, John H.

doi:10.1016/0016-7037(90)90354-n

Cited by 274 publications

(208 citation statements)

References 25 publications

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“…Because of the highly specialized nature of this model we will provide a brief explanation of its major characteristics. FREZCHEM is a Fortran version of the Spencer-Møller-Weare (1990) model. This model is based on chemical thermodynamic principles and is parameterized for the Na-K-Mg-Ca-Cl-SO 4 -H 2 O system over the temperature range from 219 k to 298 K. A recent modification of FREZCHEM includes a Gibbs energy minimization algorithm for estimating the thermodynamically stable compositions (Mironenko and others, 1997).…”

Section: Approach To the Problemmentioning

confidence: 99%

The role of carbonates in the evolution of early Martian oceans

Morse¹

1999

American Journal of Science

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ABSTRACT. Central to the question of life on Mars is whether there has been liquid water on the martian surface and how the planet could have evolved from possible initial warm and wet conditions to the cold and dry present state. Virtually all models for this climatic evolution rely strongly on the removal of an initial thick carbon dioxide atmosphere by precipitation of carbonate minerals from surface waters that may have been quite similar to those of Hadean Eon Earth's oceans. In order for this to occur, a hydrologic cycle would be necessary in which chemical weathering of silicate rocks consumes CO 2 that precipitates as carbonates in an acidic martian ocean which probably had a very high alkalinity. The consumption of atmospheric CO 2 by this process would result in a gradual decrease of the atmospheric greenhouse influence and cooling of the climate.Once the surface of Mars became cold enough so that freezing conditions prevailed, the hydrologic cycle would largely cease, and the uptake of CO 2 by silicate rock weathering would greatly diminish. The alkalinity of the freezing seawater would probably be sufficient to result in the removal of all calcium as calcium carbonate. Some magnesium and sodium would also likely be removed as carbonates as well. The removal of these cations as carbonates has a major influence on the final temperature at which liquid brines would be able to persist on the surface of Mars. During the period of freezing, the oceans would act as a source of CO 2 rather than a sink, further slowing the rate of climate change on Mars.

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Section: Approach To the Problemmentioning

confidence: 99%

The role of carbonates in the evolution of early Martian oceans

Morse¹

1999

American Journal of Science

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“…Additional work has centred on developing variable temperature models below 298.15 K, which have increased applicability to a number of diverse geochemical systems (Spencer et al, 1990;Marion and Farren, 1999). The following equations, which are described in the literature (Pitzer 1992), are the main expressions related to the solubility calculation of this model.…”

Section: Ion-interaction Modelmentioning

confidence: 99%

“…The Debye-Hückel parameter A ø = 0.385646 at 288.15 K was obtained from the literature (Spencer et al, 1990). The Pitzer binary parameters for MgBr 2 , and the mixing parameters 4 Br,SO θ were calculated from the temperature-dependent equations presented in the literature (Christov, 2011;Christov, 2012b).…”

Section: Model Parameterizationmentioning

confidence: 99%

“…The Pitzer binary parameters for MgBr 2 , and the mixing parameters 4 Br,SO θ were calculated from the temperature-dependent equations presented in the literature (Christov, 2011;Christov, 2012b). The Pitzer binary parameters for MgSO 4 can be gotten from the literature (Spencer et al, 1990;Marion and Farren, 1999), but the parameter β (2) for MgSO 4 is not mentioned in the literature (Spencer et al, 1990). Therefore, the parameters for MgSO 4 used in this study were calculated using the literature (Marion and Farren, 1999).…”

Section: Model Parameterizationmentioning

confidence: 99%

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Solubility measurement and solid-liquid equilibrium model for the ternary system MgBr2 + MgSO4 + H2O at 288.15 K

Huang

Meng

et al. 2014

Braz. J. Chem. Eng.

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-The solubility of magnesium minerals and the refractive index of the ternary system MgBr 2 + MgSO 4 + H 2 O at 288.15 K were investigated using an isothermal dissolution method. It was found that there are two invariant points in the phase diagram and the solubility isotherm of this ternary system consists of three branches, corresponding to equilibrium crystallization of Epsomite (MgSO 4 ·7H Mg,Br,SO ψ at 288.15 K was fitted using the Pitzer theory and Harvie-Weare (HW) approach. In addition, the average equilibrium constants of the stable equilibrium solids at 288.15 K were obtained by a method using the activity product constant. A chemical model, which combined the Pitzer parameters and the average equilibrium constants, was constructed to calculate the solid + liquid equilibria in the ternary system MgBr 2 + MgSO 4 + H 2 O at 288.15 K. The model agreed well with the equilibrium solubility data for the magnesium salts.

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“…• A low temperature (-54 o C ≤ T ≤ 25 o C) model for the Na-K-Ca-Mg-Cl-SO 4 -H 2 O system (Spencer et al, 1990).…”

Section: Frachem Simulationsmentioning

confidence: 99%

Modeling brine-rock interactions in an enhanced geothermal systemdeep fractured reservoir at Soultz-Sous-Forets (France): a joint approachusing two geochemical codes: frachem and toughreact

André¹,

Spycher²,

Xu³

et al. 2006

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EXECUTIVE SUMMARYThe modeling of coupled thermal, hydrological, and chemical (THC) processes in geothermal systems is complicated by reservoir conditions such as high temperatures, elevated pressures and sometimes the high salinity of the formation fluid. Coupled THC models have been developed and applied to the study of enhanced geothermal systems (EGS) to forecast the long-term evolution of reservoir properties and to determine how fluid circulation within a fractured reservoir can modify its rock properties. In this study, two simulators, FRACHEM and TOUGHREACT, specifically developed to investigate EGS, were applied to model the same geothermal reservoir and to forecast reservoir evolution using their respective thermodynamic and kinetic input data. First, we report the specifics of each of these two codes regarding the calculation of activity coefficients, equilibrium constants and mineral reaction rates. Comparisons of simulation results are then made for a Soultz-type geothermal fluid (ionic strength ~1.8 molal), with a recent (unreleased) version of TOUGHREACT using either an extended Debye-Hückel or Pitzer model for calculating activity coefficients, and FRACHEM using the Pitzer model as well.Despite somewhat different calculation approaches and methodologies, we observe a reasonably good agreement for most of the investigated factors. Differences in the calculation schemes typically produce less difference in model outputs than differences in input thermodynamic and kinetic data, with model results being particularly sensitive to differences in ion-interaction parameters for activity coefficient models. Differences in input thermodynamic equilibrium constants, activity coefficients, and kinetics data yield differences in calculated pH and in predicted mineral precipitation behavior and reservoir-porosity evolution. When numerically cooling a Soultz-type geothermal fluid from 200°C (initially equilibrated with calcite at pH 4.9) to 20°C and suppressing mineral precipitation, pH values calculated with FRACHEM and TOUGHREACT/ Debye-Hückel decrease by up to half a pH unit, whereas pH values calculated with TOUGHREACT/Pitzer increase by a similar amount. As a result of these differences, calcite solubilities computed using the Pitzer formalism (the more accurate approach) are up to about 1.5 orders of magnitude lower. Because of differences in Pitzer ion-interaction parameters, the calcite solubility computed with TOUGHREACT/Pitzer is also typically about 0.5 orders of magnitude lower than that computed with FRACHEM, with the latter expected to be most accurate.In a second part of this investigation, both models were applied to model the evolution of a Soultz-type geothermal reservoir under high pressure and temperature conditions. By specifying initial conditions reflecting a reservoir fluid saturated with respect to calcite (a reasonable assumption based on field data), we found that THC reservoir simulations with the three models yield similar results, including similar trends and amounts of reservoir po...

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The prediction of mineral solubilities in natural waters: A chemical equilibrium model for the NaKCaMgClSO4H2O system at temperatures below 25°C

Cited by 274 publications

References 25 publications

The role of carbonates in the evolution of early Martian oceans

The role of carbonates in the evolution of early Martian oceans

Solubility measurement and solid-liquid equilibrium model for the ternary system MgBr2 + MgSO4 + H2O at 288.15 K

Modeling brine-rock interactions in an enhanced geothermal systemdeep fractured reservoir at Soultz-Sous-Forets (France): a joint approachusing two geochemical codes: frachem and toughreact

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