The ball plunger (patent #6148923) combined with a spiral grooving is known as a shuttle ball plunger. The ball plunger combined with a pad plunger is called a pad/ball plunger (US#7243730 and Canadian #2,592,839C). The ball plunger combined with a disc seal is known as a disc plunger (#6148923). The disc seal can be used in conjunction with a ball or a shift rod by-pass. The casing plunger must be combined with a shift rod valve or a hydrostatic valve internally.
Numbers 1 and 2 are similar in that both well types have plenty of gas available such that a high efficiency plunger is not a requirement. Neither well type respond favorably to a shut-in period. Because the Shuttle Ball Plunger can return to the bottom of the tubing quickly, even against flow, it is used in high flow-rate wells that do not require a shut-in period for pressure building. Therefore, when using a gas-lift set-up, the compressor is not required to recirculate for an excessive length of time while using less gas to lift the same amount of fluid. The typical shut-in time for the flow line to be shut-in is 1 minute, instead of 45 minutes or more with a conventional plunger.
If the formation is high volume but low pressure, then the smallest amount of fluid down-hole will depress gas flow to the surface. Using a conventional plunger is not always the solution because, during the shut-in period, even more fluid is collected atop the formation by the wiping action of the conventional plunger. The shuttle ball plunger does not require a shut-in of any duration; therefore any water strung along the tubing string will not automatically be collected and pushed downward by the Shuttle Plunger. Plus, with the quick return trip, up and down of the Shuttle Plunger, not much fluid remains idly within the tubing. Therefore, the low pressure formation is not retarded in its gas flow to the surface.