Wikipedia
A plunger lift is an artificial lift method of deliquifying a natural gas well. A plunger is used to remove contaminants from productive natural gas wells, such as water (in liquid, mist, or ice forms), sand, oil and wax.
The basics of the plunger is to open and close the well shutoff valve at the optimum times, to bring up the plunger and the contaminants and maximize natural gas production. A well without a deliquification technique will stop flowing or slow down and become a non-productive well, long before a properly deliquified well.
The plunger lift has low energy cost, low environmental impact, low capital investment and low maintenance cost. Modern wellhead controllers offer a variety of criteria to control the plunger. The original controllers were just timers, with fixed open and close cycles.
Measuring the various pressures in the system allows intelligent and reactive control. The pressures often measured are casing, tubing, line, and differential (DP). The other items measured are plunger arrival times, flow rates, temperatures and status of various auxiliary equipment: oil tank level, compressor status.