PHREEQC (and Reaktoro) training courses

1. PRESENTATION OF THE PHREEQC (GRAPHICAL) USER INTERFACES, AND ‘ECOSYSTEM’
2. DATABASE
• Structure, syntax and conventions
• Aqueous activity models (1) : Debye-Hückel’s derived (B-dot), for dilute aqueous solutions
• Gaseous activity (fugacity) & PVTx model : Peng Robinson Equation of State (PR EoS)
• Thermochemical data : equilibrium constants of reactions (K) dependency to temperature and pressure
• Specific molar volume of aqueous species and aqueous solution volume
• Aqueous activity models (2) : ion-association ones (SIT & Pitzer), for concentrated aqueous solutions
3. GAS-WATER-SOLID (THERMODYNAMIC) EQUILIBRIA CALCULATIONS WITH PHREEQC (AND WITH A BIT OF REAKTORO)
• Water speciation with both PHREEQC and Reaktoro
• Acid-base (pH), redox (pe/Eh) and complexation
• Saturation indices with respect to solids and gas fugacities/partial pressures
• Water-solid equilibria
• Water-gas equilibria
• Ideal versus real gases (ideal gas law versus PR EoS)
• “Explicit” or “implicit” gas phase
• Concentration versus pH (Sillen or Bjerrum) diagram creating
• Waters mixing

The aim of the course is to learn in the use of PHREEQC to simulate gas-water-solid interactions (geo)chemistry under thermodynamic equilibrium, and waters mixing (still under equilibrium). An introduction in the use of Reaktoro (by simulating aqueous solutions speciation) will be also given. With the practical examples, participants will be made aware of (geo)chemical questioning in the areas of Carbon Capture and Storage (CCS), natural hydrogen, storage of hydrogen in aquifers, acidic leaching in hydrometallurgy, and barite precipitation (sulfate scaling in oil recovery by water injection).

The course will begin by the presentation of the two available PHREEQC (graphical) user interfaces ((G)UI), and of the software ‘ecosystem’. The course covers the calculation of gas-water-solid systems thermodynamic equilibria, as well as the simulation of aqueous solutions mixing (still under equilibrium assumption). A first module will be dedicated to the presentation of the PHREEQC databases, and to the notions of ideal versus real aqueous solutions and gases. Then, water speciation and gas-water-solid equilibria calculations will be taught. A last module will be dedicated to aqueous species activity calculation by the ion-association models SIT (Specific ion Interaction Theory) and Pitzer, suitable for high ionic strength aqueous solutions (brines). The rules for writing input files (scripts) as well as the different output options offered by PHREEQC will be presented. The core of the course will be the practice through running of simulation examples involving aqueous solutions ((geologic) formation waters, acidic solutions, …), CO₂, H₂, natural & synthetic (cementitious) minerals, …. When needed, the theory behind PHREEQC – i.e. the laws and physical-chemical concepts coded in the program – will be presented.