Sedimentary clay reactions

[Craig]

Hi I'm a new user to GWB and I wanted to do a simple simulation reacting a suite of minerals (illite, smectite, chlorite, chlorite/smectite, illite/smectite, muscovite, kaolinite, glauconite, quartz, calcite, dolomite, K-feldspar, anhydrite) in a subsurface resevoirs with supercritical CO2 (P = 8 - 13.5 MPa) - corresponding to reservoir temp of T ~ 35-65 C - in a brine with pH = 5 - 7 and TDS range of 18,000 - 58,000 mg/L.

 

How would I go about comparing these mineral reactions?

[Tom Meuzelaar]

Hi I'm a new user to GWB and I wanted to do a simple simulation reacting a suite of minerals (illite, smectite, chlorite, chlorite/smectite, illite/smectite, muscovite, kaolinite, glauconite, quartz, calcite, dolomite, K-feldspar, anhydrite) in a subsurface resevoirs with supercritical CO2 (P = 8 - 13.5 MPa) - corresponding to reservoir temp of T ~ 35-65 C - in a brine with pH = 5 - 7 and TDS range of 18,000 - 58,000 mg/L.

 

How would I go about comparing these mineral reactions?

 

Hi Craig:

 

Your question is fairly broad in scope, so I will point you in 3 general directions. Other users that have expertise with systems of your type may wish to fill in additional details:

 

• For reacting a suite of minerals, a good place to start is the Reaction Modeling guide, p.13, with the section on titration paths.
  
• The default thermodynamic database in GWB has an upper temperature limit of 300C and is configured for 1atm. Some have gone to the effort of extending them to higher pressures, but for the lithostatic pressures of most geologic applications, changes in the log K values for (most) data at higher pressures are insignificant relative to the inherent error range in the default log K measurements.
  
• For high salinity datasets (ionic strength > .3), you'll need to make a choice as to which activity model you are going to be using. The default database uses an extended form of the Debye-Huckel, but GWB comes with datasets that allow you to use Pitzer formulations as well. However, the datasets for higher ionic strengths have significant limitations, and should be used with great caution because of the empirical nature of the virial techniques employed. You will want to refer to the Essentials Guide, p. 68.
  

 

I hope this is of help.

 

Tom Meuzelaar

RockWare, Inc.