Continuous injection is the most common method of gas lift. High pressure gas is injected continuously down the annulus, through a gas lift valve, and into the tubing, creating a lightened fluid gradient, reduction of wellbore pressure on the formation, which results in drawdown between the wellbore and formation. This drawdown allows the formation to produce desired fluids.
Intermittent injection is a method of gas lift (typically combined with plunger lift ALS) where gas is intermittently injected, allowing the formation to build pressure while injection is diverted to another well or circulated. Fluids build up in the tubing, well bore pressure builds, and a diversion of gas back to the well lifts the fluid slug to surface. The well is shut-in and process is then repeated.