1. n. [Well Completions]

An artificial-lift method principally used in gas wells to unload relatively small volumes of liquid. An automated system mounted on the wellhead controls the well on an intermittent flow regime. When the well is shut-in, a plunger is dropped down the production string. When the control system opens the well for production, the plunger and a column of fluid are carried up the tubing string. The surface receiving mechanism detects the plunger when it arrives at surface and, through the control system, prepares for the next cycle.

See: production string

2. n. [Production Testing]

A type of gas-lift method that uses a plunger that goes up and down inside the tubing. The plunger provides an interface between the liquid phase and the lift gas, minimizing liquid fallback. The plunger has a bypass valve that opens at the top of the tubing and closes when it reaches the bottom. Plunger-lift methods are used to remove water and condensate from a well, but they can handle only a limited column of liquid. Typically, these methods are applied on gas wells with high gas liquid ratio (GLR) to operate only with formation gas.