Well Test Analysis in Naturally Fractured Gas Condensate Reservoirs Below Dew Point Pressure

摘要

Gas condensate reservoirs below dew point pressure have been the subject of many studies in the petroleum literature. These studies investigated the impact of the resulting liquid condensate drop-out on well performance and concentrated mainly on reservoirs with homogeneous behaviors.This paper focuses on the effect of condensate drop-out in naturally fractured carbonate reservoirs with double porosity behaviors and on the changes in well test responses due to changing oil/gas relative permeabilities. Specifically, this paper examines the impact on the storativity ratio (w) and the interporosity flow coefficient (λ) below the dew point pressure as the radius of the condensate bank increases away from the wellbore. By generating well test responses under different operational well conditions below the dew point pressure, the paper shows that λ decreases due to two-phase flow in the reservoir, whereas w shows very little change. The condensate bank appears as an additional skin effect, as in reservoirs with homogeneous behavior. This skin can be removed temporarily by hydraulic fracturing.Conclusions of the paper are verified with well test data from a carbonate formation in the Middle East and compositional simulation models.