Abstract: To improve the recovery of condensate oil is the primary purpose to develop gas condensate reservoir. Gas injection can prevent condensate oil from separating out from gas condensate reservoir. The PVTCOG application software developed by our-selves and the PR state equation were employed in a real closed condensate gas reservoir to study the depletion performance in different production stages, the influence of dry gas, the nitro-gen and carbon dioxide on the dew point pressure, the gas injec-tion time, the condensate oil reserve and the condensate oil re-covery. The results showed that: different injection gas has dif-ferent impact on dew point pressure; with more gas injection the condensate oil reserve will come down while the condensate oil recovery will go up; the optimum time for gas injection is not
necessarily at pressure higher than dew point pressure.

Key words: gas condensate reservoir, gas injection, con-densate oil, recovery factor