A new method to calculate the in-situ compositions of gas condensate reservoirs

Abstract

ABSTRACT The well fluid composition of a gas condensate reservoir varies significantly during depletion. Therefore, the samples taken from the well stream may not be representative of the in-situ fluid compositions of gas condensate reservoirs. Other than putting the field development plan into risk based on PVT analysis of the unrepresentative samples, it is essential to reconstruct the initial fluid composition. A new method is proposed in this study to determine the in-situ compositions of gas condensate reservoirs. Multi-objective genetic algorithm and compositional numerical simulations are applied to calculate the initial composition by fitting two objectives: (1) the absolute deviation of the compositions between simulation results and the sample taken at any stage of depletion; (2) the history matching results between compositional simulations and well production performance. A case study of a near-critical gas condensate reservoir with two sampling results is also performed to validate the new method in this paper. The results show that the total absolute deviations of sampling compositions are 6.93–10.03 mol% and the relative deviation of cumulative production is 2.71%.