Abstract: The biggest problem in the development process of condensate gas reservoirs is the condensate loss resulted from the fact that the formation pressure is lower than the dew point. Gas injection is a good method of preventing the condensate from precipitating and improving the oil recovery factor. However, so far there has been no systematic investigation on the effect of different injection media on the condensate gas facies. Taking an example from a true condensate gas reservoir and using the self-developed PVTCOG program and PR state equation, this paper studied and correlated the influence of dry-gas injection,nitrogen injection and CO₂ injection on the condensate gas factes at different constant drainage stages in condensate gas reservoirs. The study showed that different gases can significantly affect the dew point of condensate gas, condensate saturation and recovery factor.

Key words: Condensate gas, condensate, gas injection, phase state, dew point