TABLE OF CONTENTS Plunger lift is an intermittent artificial lift method that usually uses only the energy of the reservoir to produce the liquids. A plunger is a free-traveling piston that fits within the production tubing and depends on well pressure to rise and solely on gravity to return to the bottom of the well. Figure 7-1 illustrates a typical plunger lift installation.
Plunger lift operates in a cyclic process with the well alternately flowing and shut-in. During the shut-in period with the plunger on the bottom, gas pressure accumulates in the annulus, and liquids have mostly already accumulated in the well during the last portion of the flow period. Liquids accumulate in the bottom of the tubing, and the plunger falls through the liquids to the bumper spring to await a pressure buildup period. The pressure of the annulus gas depends on the shut-in time, reservoir pressure, and permeability. When the annulus pressure increases sufficiently, the motor valve is opened to allow the well to flow. The annulus gas expands into the tubing, lifting the plunger and liquids to the surface, with some help from the producing gas.
The reservoir is allowed to produce gas until the production rate decreases to some value near the critical rate and until liquids begin to accumulate in the wellbore. The well is then closed, and the plunger falls back to the bumper spring first through gas and then through some accumulated liquid.
The pressure buildup period...
