Method and apparatus for producing a first zone through a wellbore while simultaneously injecting gas into a second zone through the same wellbore. The production stream is produced to the surface through a string of tubing where gas is separated therefrom. The separated gas and/or gas from another source is then mixed with a carrier fluid (e.g. produced water, etc.) to form a mixture which, in turn, is pumped down the well annulus and through a downhole separator (e.g. an inverted hydrocyclone) where at least a portion of the gas is separated from the mixture. The separated gas is injected into the second zone while the remaining mixture is commingled with the production stream before the combined streams flow to the surface through the tubing.