How can i investigate the interaction between gas-rock or gas-water-rock in phre

[Zhanus]

I want to investigate the reaction between a mineral (Calcite) and a gas phase (H2) which has been stored at a depleted gas reservoir.
I try to model this by defining a solution and put H2(g) as equilibrium phase and defining a Reaction by Calcite, but it doesn't give me a reasonable result.
I really appreciate if some one can help me with this

[dlparkhurst]

Here is an example simulation where calcite is maintained at equilibrium as H2 is added to solution. It models a kinetic reaction of H2 with calcite to produce CH4. A fixed pressure gas phase is included; although H2 is not initially present. Essentially, according to thermodynamics, calcite and H2 will not coexist.

Code: [Select]

SOLUTION
EQUILIBRIUM_PHASES
Calcite 0 10
GAS_PHASE
-fixed_pressure
CO2(g) 0
H2(g)  0
CH4(g) 0
REACTION_PRESSURE
10
REACTION
H2 1
1 in 10
USER_GRAPH 1
    -headings               rxn CH4(g) pH
    -axis_titles            "H2 added, moles" "CH4 gas, moles" "pH"
    -initial_solutions      false
    -connect_simulations    true
    -plot_concentration_vs  x
  -start
10 GRAPH_X RXN
20 GRAPH_Y GAS("CH4(g)")
30 GRAPH_SY -LA("H+")
  -end
    -active                 true
END