Bypass or Freecycle Plunger Lift Systems
Bypass plungers are meant for “good” wells. This plunger type is dependent on gas rate instead of build pressure. Since the advantage to running these plungers is greatly reduced shut in times, the well does not build enough pressure to cycle the plunger. The rule of thumb for successful operation is that the well MUST produce a minimum of 70% of the surface critical rate.
There are two types of Bypass plungers: Continuous Flow and Quick Falling.
Continuous Falling plungers are designed to fall against flow. These are wells that have just started showing signs of liquid loading and by “sweeping” the tubing walls of accumulating fluid the well will continue to flow naturally.
Quick Falling plungers are designed for good wells that are operating at the minimum gas requirement (70% of surface critical rate). These wells require a very short shut in time to overcome low gas velocities due to liquid loading. Where a Conventional plunger may require a minimum of 45 minutes of shut in time to fall and build pressure, these wells may only require 10 – 20 minutes. Therefore, the Quick Falling plunger has been designed to fall at a much faster rate to get to the bottom hole spring. These plungers will typically fall at rates of approximately 700 – 900 ft/min.
The most important operating parameter for these plungers is After Flow. Similar to a Conventional plunger lift, once the plunger has lifted the fluid to the surface the well must be given some time to accumulate fluid for the next cycle.
Note: Due to the bypass areas of these plungers, it is highly recommended that an auto-catch assembly be run. This will ensure that the plunger is held in the lubricator until the controller signals the plunger to fall. Failure to run the auto-catch may result in reduced gas rates, due to the plunger restricting flow, and possible dry cycling of the plunger.