The ongoing need for greater operational cost efficiency has encouraged oil companies to seek new methods that can simplify completion processes and reduce the number of required well interventions. This focus has resulted in new challenges for engineering/manufacturing and service companies to develop multi-functional equipment. To meet these challenges, a new generation of completion equipment with capabilities that would have been considered impossible ten years ago has been introduced to the oilfield. This equipment has been designed to not only reduce the number of interventions normally required in traditional completion scenarios but also to meet challenges of safety and reliability that can surpass the cost of contingency measures should the product fail.
The development of one such device, the "disappearing plug," which serves as a plugging device for setting a hydraulic-type packer, will be the focus of this paper. When run in with the completion, the tubing will fill automatically through an auto-fill device, and then, will close during one of the pressure cycles. The fluid-expendable plug material disintegrates on the last pressure cycle, which allows full-tubing-drift production and eliminates the need for a slickline or coiled-tubing run to retrieve a plugging device as would be the case with conventional methods.
While the industry average for successful installation of interventionless devices has still not reached the sought-after 100% reliability, when these concepts have been successful, the expected economic job goals have been surpassed.When successful in offshore, horizontal, and/or high angle wells where slickline or coiled tubing intervention after completion is significantly more costly, these interventionless technologies have proven to be even more beneficial.
The paper will discuss development of the plug, some of the failures that occurred, how these difficulties were addressed, and finally, will discuss several recently run installations. These clearly show the extent of the economic benefit that can be realized.
Disappearing plug technology currently improves economics by eliminating the need for slickline and coiled-tubing interventions in plugging operations. When setting hydraulic packers, this not only reduces operating costs but also the risks associated with interventions and plug failures. One of its most significant contributions, however, becomes apparent when considering the future trends of the industry—interventionless and intelligent well technologies. The disappearing plug will undoubtedly play an important role in the actualization of these future well trends.
For many years, the oil industry has sought out ways to incorporate new completion devices that do not require intervention to complete the well.1,2,3,4 Minimizing or eliminating this need can reduce completion and operating costs significantly, particularly in offshore, high-angle, and horizontal completions where slickline or coiled-tubing intervention are often more costly and pose greater operational risks.
Developing interventionless devices that can overcome adverse well conditions has presented many challenges, and thus, the devices usually have been limited to single-function operation. Most of them are mechanical in design but limited-life, battery-operated electronic components are often included in the designs. The mechanical devices are generally controlled with hydrostatic pressure and applied pressure pulses from the surface. Acoustic and electro-magnetic actuation techniques have also been explored for manipulating these devices.