Given a mixture of oil and gas under pressure
p and temperature
T with
a total mass of oil component
m_O = m_{Oo}(p,T) + m_{Og}(p,T)
total mass of gas component
m_G = m_{Gg}(p,T) + m_{Go}(p,T)
then
the mass share of oil component in oil phase
m_{Oo}(p,T)
the mass share of gas component in gas phase
m_{Og}(p,T)
the mass share of gas component in oil phase
m_{Go}(p,T)
mass share of gas component in gas phase m_{Gg}(p,T)
are all functions of pressure p and temperature T.