Validation and Recalibration of the Solubility Models in Support of the Heater Test in Salt Formations

Journal Article · 23 January 2020 · MRS Advances

DOI: https://doi.org/10.1557/adv.2020.42 · OSTI ID:1618087

Xiong, Yongliang ^[1]; Kuhlman, Kristopher L ^[1]; Mills, Melissa Marie ^[1]; Wang, Yifeng ^[1]

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1. Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

The US Department of Energy Office of Nuclear Energy is conducting a brine availability heater test to characterize the thermal, mechanical, hydrological and chemical response of salt at elevated temperatures. In the heater test, brines will be collected and analyzed for chemical compositions. In order to support the geochemical modeling of chemical evolutions of the brines during the heater test, we are recalibrating and validating the solubility models for the mineral constituents in salt formations up to 100°C, based on the solubility data in multiple component systems as well as simple systems from literature. In this work, we systematically compare the model-predicted values based on the various solubility models related to the constituents of salt formations, with the experimental data. As halite is the dominant constituent in salt formations, we first test the halite solubility model in the Na-Mg-Cl dominated brines. We find the existing halite solubility model systematically over-predict the solubility of halite. We recalibrate the halite model, which can reproduce halite solubilities in Na-Mg-Cl dominated brines well. As gypsum/anhydrite in salt formations controls the sulfate concentrations in associated brines, we test the gypsum solubility model in NaCl solutions up to 5.87 mol•kg^–1from 25^°C to 50^°C. The testing shows that the current gypsum solubility model reproduces the experimental data well when NaCl concentrations are less than 1 mol•kg^–1. However, at NaCl concentrations higher than 1, the model systematically overpredicts the solubility of gypsum. In the Na⁺—Cl^–—SO₄^2–—CO₃^2–system, the validation tests up to 100^°C demonstrate that the model excellently reproduces the experimental data for the solution compositions equilibrated with one single phase such as halite (NaCl) or thenardite (Na₂SO₄), with deviations equal to, or less than, 1.5 %. The model is much less ideal in reproducing the compositions in equilibrium with the assemblages of halite + thenardite, and of halite + thermonatrite (Na₂CO₃•H₂O), with deviations up to 31 %. The high deviations from the experimental data for the multiple assemblages in this system at elevated temperatures may be attributed to the facts that the database has the Pitzer interaction parameters for Cl^–—CO₃^2–and SO₄^2–—CO₃^2–only at 25^°C. Finally, in the Na⁺—Ca²⁺—SO₄^2–—HCO₃^–system, the validation tests also demonstrate that the model reproduces the equilibrium compositions for one single phase such as gypsum better than the assemblages of more than one phase.

• Research Organization: Sandia National Laboratories (SNL-NM), Albuquerque, NM (United States)
• Sponsoring Organization: USDOE Office of Nuclear Energy (NE), Fuel Cycle Technologies (NE-5)
• Grant/Contract Number: AC04-94AL85000; NA0003525
• OSTI ID: 1618087
• Report Number(s): SAND--2019-13233J; 680934
• Journal Information: MRS Advances, Journal Name: MRS Advances Journal Issue: 5-6 Vol. 5; ISSN 2059-8521
• Publisher: Materials Research Society (MRS)Copyright Statement
• Country of Publication: United States
• Language: English