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This term usually refers to wells, which are being intermitted with the use of a Controller and Motor Valve. The well is simply opened and closed using time and/or casing and tubing pressure. The well is shut-in to allow casing pressure build-up and fluid entry into the annulus. After this shut-in time, and pressure requirements are met and the controller opens the motor valve allowing the well to produce until a drop in casing pressure requires another shut-in period. This method of producing can be very beneficial on a well, which has trouble flowing against high line pressure. This additional build-up will sometimes overcome a high line pressure / low casing pressure situation.

Plunger Lift Operations

Most wells, which will see an increase in production by "Intermitting”, will also see an additional increase by installing a mechanical interface in the tubing between the gas and liquid. This interface is called a plunger. The plunger travels the entire length of tubing. When the well is shut-in, the plunger falls to the bottom and awaits the casing pressure build-up and/or time requirements. When the well opens, the plunger travels to the surface bringing with it the liquid accumulated above it. This plunger eliminates a large percentage of the fluid loss characteristic of vertical flow of gas and liquid in tubing. This fluid loss is referred to as "Fall-Back". The percentage of fluid loss will vary with well and formation variables. A reliable estimate of loss is about 7% per thousand feet of vertical lift. A Plunger will also help reduce paraffin and scale build-up in the tubing.

Controller Functions

Open Time

The time which keeps the well open and flowing. This must be at least long enough to allow for plunger arrival. It must also allow time for adequate flow rates from the well.

Close Time

This is the time when the motor valve is closed and all vertical flow in the well has stopped. This setting must satisfy several conditions. Some of which are the following:
1. Plunger Fall Time- The plunger must have adequate time to fall from the surface to the bottom of the tubing. This time can be calculated by dividing the plunger fall speed by the depth of the tubing. The plunger will fall an average of 250 feet per minute. This is an average of dry tubing, fluid, and pockets of fluid strung up and down the tubing string.
2. Casing Pressure Build-Up- The casing must have adequate time to recover the pressure and gas volume which was utilized in the last plunger cycle. This is necessary to insure the next cycle is successful .

Plunger Lift Terms

Afterflow Time

After-Flow is used to sell gas after plunger arrival. A lot of oil wells are "shut-in-on-arrival" as casing gas pressure and volume are critical to the next cycle. However in gas well operation the fluid must be lifted out of the well and gas sold after plunger arrival for efficient operation. An "ESO" or plunger arrival sensor is utilized in conjunction with the well-head controller to sense plunger arrival at the surface. A Delay time can now be set to close the motor valve to ensure efficient operation. An example might be that the operator knows that 71/2 minutes is the average plunger run time but he or she wants to sell gas for 45 minutes after arrival. The operator might then put in 30 minutes of open time with a 45 minute delay. Now regardless of how low the plunger takes to arrive the well will sell gas for 45 minutes after plunger arrival then the controller will close the motor valve.

Back-Up Time

When a plunger cycle is missed due to high line pressure, flow line freeze, or for whatever reason it normally means the well is loaded or partially loaded. To ensure the next cycle is successful the operator might want to put in additional close or build-up time. This is referred to as back-up time. An example is an open time of one hour, close time three hours, and a back-up time of six hours. After the back-up time is satisfied the controller will resume normal operation.

Fall Time

This is a close time function that ensures no inputs to the controller allowing nothing to happen while the plunger is falling. This ensures the plunger will always get to the bottom of the tubing before the opening of the motor valve.