Current Status of the EQ3/6 Software Package for Geochemical Modeling

Wolery, Thomas J.; Jackson, Ken; Bourcier, William L.; Bruton, C.J.; Viani, B.E.; Knauss, Kevin G.; Delany, J.M.

doi:10.1021/bk-1990-0416.ch008

Cited by 136 publications

(104 citation statements)

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“…We expect that upscaling is likely more difficult for natural sub-surface sandstone with hierarchical physical and geochemical heterogeneity structures. (Wolery et al [1990]). Makes use of the extended Debye-Huckel model for activity corrections.…”

Section: Discussionmentioning

confidence: 99%

“…In the effluent, DIC was estimated by assuming that the stirred reactors behaved as closed systems in which calcium carbonate was the only phase precipitated such that ΔCa = ΔDIC (Table 2). Saturation indexes for the well-mixed effluent were calculated with the code CrunchFlow, which makes use of the EQ3 database (Wolery et al [1990]). Activity coefficients are calculated with the extended Debye-Hückel equation.…”

Section: Continuously-stirred Precipitation Rate Experimentsmentioning

confidence: 99%

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Upscaling calcium carbonate precipitation rates from pore to continuum scale

et al. 2012

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The upscaling of calcite precipitation rates in porous media from the pore (micron) to continuum (centimeter) scale is evaluated with an integrated experimental and modeling approach. Experiments using cylindrical cores packed with glass beads and calcite (Iceland spar) crystals were injected over a period of 28 days with a supersaturated mixture of CaCl 2 and NaHCO 3 to induce calcite growth. Bulk rates of precipitation based on the change in aqueous chemistry over the length of the column are compared with spatially resolved determinations of carbonate precipitation using X-ray synchrotron microtomographic imaging at the micron scale. These data are supplemented by continuously-stirred reactor experiments using the same calcite seed material so as to minimize differences in the effects of reactive site density of the seed material, and to evaluate the rate of precipitation in the absence of transport or "porous medium" effects. Calcite precipitation rates determined in the stirred flowthrough reactor in this study are considerably slower than rates determined at similar supersaturation in unseeded batch experiments by Tang et al. [2008a], although these rates are compatible with those reported in Nehrke et al. [2007] for precipitation on Iceland spar when the same normalization to reactive surface area is used. The nearly linear dependence of the rates on supersaturation cannot be attributed to a diffusion control in the case of the stirred reactors and is likely the result of multi-sourced spiral growth.Integrated precipitation rates based on column effluent chemistry from a higher supersaturation experiment are in good agreement with determinations of total carbonate precipitated based on determination of pre-and post-experiment mass in the column using X-ray microtomography. Using the rates of precipitation determined in the well-stirred flowthrough reactors, it is possible to match the spatially-resolved microtomographic and aqueous data with a coarser resolution continuum model using volume-averaged flow and reactive surface area if the generation of new reactive surface area is accounted for. A nucleation or surface roughening event, which is most pronounced within two millimeters of the column inlet where the supersaturation is highest, is recorded by both BET analysis, which indicates an increase in specific surface area from 0.012 m 2 •g -1 to a value of 0.21 m 2 •g -1 for neoformed calcium carbonate, and by X-ray microtomography. The best fit of the column X-ray microtomography data is provided by simulating calcite precipitation either as a single nearly linear rate for multi-sourced spiral growth, or as two parallel rates that include the spiral growth model and a 2D heterogeneous nucleation model modified by a partial diffusion control, although nucleation needs to be relatively minor on a mass basis in order to match the data. The combined experiments and modeling indicate that it is possible to develop upscaled quantitative models for porous media reactivity, but changes in such propert...

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Section: Discussionmentioning

confidence: 99%

Section: Continuously-stirred Precipitation Rate Experimentsmentioning

confidence: 99%

Upscaling calcium carbonate precipitation rates from pore to continuum scale

et al. 2012

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“…The EOS also gives logf CO2 = 2.9 (in bar) and logf H2O = 1.8 for the fluid of the above composition. Using SUPCRT92 (Johnson et al, 1992) and EQ3/6 (Wolery et al, 1990), the equilibrium constant for the nahcolite formation reaction can be estimated as:…”

Section: Discussionmentioning

confidence: 99%

Nahcolite in fluid inclusions from the Ryoke metamorphic rocks and its implication for fluid genesis

Hoshino

Nagatomi²,

Watanabe

et al. 2006

Journal of Mineralogical and Petrological Sciences

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Nahcolite (NaHCO 3 ) has been found in fluid inclusions in quartz veins hosted by the Ryoke metamorphic rocks in Kasado Jima (Island), Yamaguchi Prefecture, Japan. The inclusions are classified into three types: type 1 containing vapor +/− liquid of the H 2 O NaCl CO 2 CH 4 system, type 2 of H 2 O NaCl fluids and type 3 with nahcolite solid. Salinities of the nahcolite bearing fluids are lower than 4 wt% NaCl eq. Extremely large volume fractions of nahcolite solids, occupying more than 50% of total inclusion volume, and various fluid compositions are indicative of their origin as accidentally trapped ones while the fluids were immiscible below the nahcolite melting temperature (270 °C). A thermodynamic calculation of the nahcolite stability and a phase analysis of the fluids show loga Na + = 7.4 -pH as the minimum activity at P = 100 MPa and T = 270 °C where the neutral pH = 5.6. Hence, it can be concluded that the original (prior to immiscible state) liquids might have contained high Na + and low Cl − yielded by an interaction of a low salinity fluid and Na bearing minerals such as plagioclase in the host metamorphic rocks below the fractures now occupied by quartz if nahcolite precipitated from boiling fluids.

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“…As a part of this effort, a geochemical, thermodynamic modeling program, or computer code, called EQ3/6 has been under continual development. 23,24 This program, by including data pertaining to the site such as temperature and the composition of natural waters, can be used to calculate equilibrium amounts of dissolved metals, such as actinides and fission products, that would be released by the solids contained in the nuclear waste form. However, the geochemical modeling resulting from this computer code will only be accurate when the input parameters, the standard state thermodynamic properties of the elements and their compounds, are accurate.…”

Section: Statement Of the Problemmentioning

confidence: 99%

Precipitation of neptunium dioxide from aqueous solution

Roberts¹

1999

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Current Status of the EQ3/6 Software Package for Geochemical Modeling

Cited by 136 publications

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Upscaling calcium carbonate precipitation rates from pore to continuum scale

Upscaling calcium carbonate precipitation rates from pore to continuum scale

Nahcolite in fluid inclusions from the Ryoke metamorphic rocks and its implication for fluid genesis

Precipitation of neptunium dioxide from aqueous solution

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