How to determine the Air Mass Fraction in the Initial Condition?

[XiaoMao 0]

Recently, I would like to model the Mixed gases injection process.

I have used a Extra Cell as a injection source.

However, I do not know how to determine the Air Mass Fraction.

Actually, I want to inject a hot mixed gases into a aquifer, and I have known the temperature, but I do not know the partial pressure.

Only I known is that the concentration of gas in final water, CO2 is 17mmol/kg.

So, How can I set the initial condition at the Extra Cell?

When I set the Air Mass Fraction is 0.5 or 0.55, it will stop.

      

The model can run if I set the Air Mass Fraction is 0.6, but it can not reach the final time I set.