A completion system delivers lifting gas supplied from the surface via a casing annulus through the packer for injecting to the wellbore at bottom hole. So, lifting gas maximizes hydrocarbon producing from a subterranean well while maintaining integrity and serviceability as a typical gas lift well. More specifically, a single completion system uses the same tubing string for both producing the well and delivering lifting gas to the wellbore at downhole. The top section of the tubing is used for producing the well, while the bottom section of the tubing is used for delivering lifting gas for injecting at bottom hole. The lifting gas will be injected to the wellbore proximately at perforation intervals for helping unloading liquid and producing the well. The use of modified equipment named “TK Bypass Mandrel” and “JP Bypass Nipple Sub” allows delivering and controlling of the lifting gas for injecting at bottom hole via a single tubing string.