Getting the Oil/Gas Mixture Out from the Ground
First we make a few mass balances:
 
Total Hydrocarbon Balance: 
 
 
 
Species Hydrocarbon Balance:
 
 
 
Water Balance:
 
 
 
 
Then we handle the restrictions on system:
Saturations add up to 1 
Saturation is the fraction of the V/L space that is a particular phase 
Using: 
 
 
 
 
Sl+Sw+Sv=1
 
And: 
 L=Total moles of liquid/pore volume 
 V=Total moles of vapor/pore volume 
 
V=Sv*rhov
L=Sw*rhow 
 
The restriction is:
 
 
 
Use the perfect gas law and the compressiblity factor.
In equilibrium, each phase has the same temperature and pressure 
 
 
 
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