In BO and MBO PVT models when oil and gas phases reach chemical equilibrium the total mass of oil and gas components spread between oil and gas phases according to ambient pressure p and temperature T.
Given a mixture of oil and gas sharing the same volume under pressure
p and temperature
T with
the total mass of oil component m_O = m_{Oo}(p,T) + m_{Og}(p,T)
the 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 oil 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.
The quantitative measure of cross-phase exchange is given by Soliton GOR ( R_s) and Vaporized Oil Ration ( R_v):