Theoretical and experimental determination of initial reservoir fluid in a lean gas condensate reservoir

• A laboratory method proposed to obtain initial gas condensate reservoir fluid.
• The proposed method was based on matching of initial GCR and dew point pressure.
• CCE and CVD tests were applied to the recombined fluid to observe its phase behavior.
• The proposed method creates a fluid with the same phase behavior as the initial fluid.

In this work, a new theoretical and experimental method has been proposed to obtain initial reservoir fluid from well head separator samples in a depleted lean gas condensate reservoir.Condensate stabilization technique (CST) is a new recombination method based on simultaneous matching of dew point pressure and gas condensate ratio of initial reservoir fluid. The proposed method is applied to a real lean gas condensate reservoir in Iran, namely Jahroom. The modified Esmaeilzadeh–Roshanfekr equation of state and the Genetic Algorithm in MATLAB environment are used to simulate the CST method. The reservoir depletion process has been simulated by the constant volume depletion test. For nine pressure steps in the CVD test the proposed method was applied on separator samples. The average absolute deviation for composition of the recombined samples was found to be less than 3.5%. The proposed method was also experimentally checked by applying on the Jahroom separator samples. The experimental results show that the absolute deviation of 3.5% for the gas–condensate ratio (GCR) and 1.72% for the dew point pressure are achieved. Additionally, the average absolute deviation for composition of the recombined sample was found to be 4%. The results of calculation and experiment show that the proposed recombination method can produce a fluid with a similar phase behavior of initial reservoir fluid with an acceptable accuracy.