A plunger-lift system is a low-cost, efficient method of increasing and optimizing production in oil and gas wells, which have marginal flow characteristics.

Functionally, it provides a mechanical interface between the produced liquids and gas. Using the well's own energy for lift, liquids are pushed to the surface by the movement of a free-traveling piston (plunger) traveling from the bottom of the well to the surface. This mechanical interface eliminates liquid fallback, thus boosting the well's lifting efficiency. In turn, the reduction of average flowing bottom hole pressure increases inflow.

Plunger travel is normally provided by formation gas stored in the casing annulus during a shut-in period. As the well is opened and the tubing pressure allowed to decrease, the stored casing gas moves around the end of the tubing and pushes the plunger to the surface. This intermittent operation is repeated several times per day.