Geochemist's Workbench Support Forum

# [OLD] Gas distribution between phases

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Subject: gas distribution between phases

I m using React for geothermal work and I have a general question about the distribution of gases between phases.

1) If I boil (remove water), do I lose gases as would occur with actual boiling?

2) I notice that when I add methane (see input file below), and then heat up the fluid, the molality of Methane(aq) changes. Where does it go?

â€œc:Program FilesGwbGtdatathermo.com.v8.r6+.datâ€?

print species = Long

decouple all

couple S

couple H

TDS=1616 mg/kg

swap H2S(aq) for O2(aq)

swap NH4+ for NH3(aq)

swap Methane(aq) for HCO3-

SiO2(aq)=509.2 mg/kg

B(OH)3(aq)=7.5 mg/kg

Na+=368.5 mg/kg

K+=57.3 mg/kg

Li+=1.82 mg/kg

Ca++=6.32 mg/kg

Sr++=0.319 mg/kg

Cl-=395.1 mg/kg

F-=14.05 mg/kg

HCO3-=61.9 mg/kg

SO4--=180.4 mg/kg

H2S(aq)=15 mg/kg

NH4+=1.65 mg/kg

Methane(aq)=0.00001 mg/kg

pH=9.45

react 112 moles H2O cuttoff=11.2

react 861.85 mmoles CO2(g) cutoff = 86.185

react 6.45 mmoles CH4(g) cuttoff = 0.645

react .347 mmoles H2(g) cuttoff = 0.0347

react 8.02 mmoles H2S(g) cuttoff = 0.802

react 1.2 mmoles NH3(aq) cuttoff = 0.120

react 23.36 mmoles N2(g) cuttoff = 2.336

T initial = 25, final = 244

precip = off

From: Craig Bethke

Subject: Re: gas distribution between phases

(1) To model boiling in an open system, you need to fix the fugacities of the gases in your fluid to those in the surrounding atmosphere. There are examples of doing this in the chapter on evaporation, in the green book.

(2) In a polythermal reaction path, mass will be redistributed among the species in solution to reflect the species' changing relative stabilities. In your case, methane reacts to form CO2 and H2. If you don't want this reaction to occur, you need to disenable the CH4/HCO3 redox couple.

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