Abstract

A general theory and a method is developed to model compositional grading and fluid saturation change within the gas-oil transition zone using a non-isothermal model for compositional grading that accounts for the modifying effect of capillary pressure on phase equilibrium (gas and oil pressures are not the same at a point). At each depth compositional grading calculations will result in the prediction of capillary pressure, and then concept of Leverett‘s J-Function will be used to calculate phase saturation.