How do I calculate water-gas-air ratio is a wellbore?

[LandoGriffin]

Hi all,
I'm trying to determine the amount of water,gas and air I have in a well. The well PBD is 691m and we tagged the fluid level at 583m. The casing is 4.5" OD (117.93 m/m3)so I know I have 0.92m3 of fluid.

The pressure has built up to 4500 kPa. I want to know how many e3m3 of gas are in the wellbore (primarily CH4) and what the ratio of air:gas is to ensure we don't have an explosive mixture when we go back in to do a workover.

I also need to calculate the water-gas ratio in m3/e3m3.

Either I'm overthinking this or missing something that should be blatantly obvious. Any thoughts?

 

[KernOily]

I don't see any way to a priori calculate the amount of air present. Air will exist in equilibrium with CH4 gas in any mole fraction you want, so you can't use a simulator/flash calculation to estimate the fractions. YOu can calculate the liquid water fraction in equilibrium with gas or air but not both - there are too many unknowns.

One way would be to get a downhole gas sample with a downhole bomb, then do a gas analysis. That would give you the fractions of air and CH4 (and everything else) in the wellbore.

Thanks!
Pete