Abstract: A downhole gas ventilation system includes a perforated tubing positioned within a production tubing installed in a wellbore. The perforated tubing couples to wellbore equipment positioned uphole of the perforated tubing within the wellbore to flow multiphase hydrocarbons received within the perforated tubing into the wellbore equipment. The perforated tubing includes two ends and a sidewall connecting the two. Multiple perforations formed in the sidewall receives the multiphase hydrocarbons within the perforated tubing. The perforated tubing outer diameter is smaller than the production tubing inner diameter. The perforated tubing facilitates separation of the liquid phase from the gaseous phase. A one-way check valve is coupled to the upper end of the perforated tubing to vent the gaseous phase that rises towards the upper end out of the perforated tubing, out of the production tubing and into an annulus defined between the production tubing and the wellbore inner wall.