This paper will review the concept, use and current developments of casing plungers since their inception in the 1980's. Their use has only recently become a significant impact in artificial lift for producers.
The use of Casing plungers as a production tool in the USA has been developing for over 10 years.They have enjoyed a limited success as a valid production tool and are very specific in application.
Their success has been limited by some practices used during completion of a well and the internal conditions of the casing in older wells. There use in strings of casing with mixed weights has been erratic. Yet, the plunger has shown some very significant results in the production of gas from some very difficult wells.
The wells that have been able to apply this method of artificial lift, once found that the safe use of the casing plunger with its positive seals to be a prime issue when the plunger is in travel to the surface.
This includes the integrity of the casing with no damage to its interior walls. The use of varied weights of casing in a well string can also be an issue of concern.
The manufacturers of the casing plunger systems have limited the travel rate or velocity of the casing plunger by connecting the flow line to a tightly restricted orifice. This restricted flow has led to criticism of the production results that can be expected. The need for change of this design has led to a more successful operation.
There had been few developments in this equipment until the past few years. An effort to improve the production of the well with assuring a safe operation has led to a effort to design and develop a system that will yield optimal results.
The goals to develop an automated control system for the casing plunger were established.
There had to be a Fail-safe control system that permits the production of a well in excess of what was possible with the current system.
It should create a longer life expectancy of the polymer seals that are affected by casing plungers cycling too often. The use of a free cycle plunger was dismissed as non-productive due to excessive wear on seals and dry runs.
The system should maintain higher production rates when the casing plunger is at surface. The seals should have a chance to stay in a low pressure lubricator to normalize.
All of these goals were to be a high priority in re-designing this system.
Most casing plunger have been set up and used with no controls or valves to intermit the flow. This made them free cycle up and down the casing with only the internal bypass valve to open and allow it to fall.
The alternative was to have the Operator close the plunger latch and trap the plunger at the surface on its next cycle to the surface. This was done to eliminate excessive cycles and the accompanying wear of the seals.
This accomplished the reduced wear on the seals but allowed wells to be able to load up with liquids beyond their ability to overcome. This meant that they set with little or no flow until the casing plunger was released and cycled.