The objective of this paper is to examine the recent improvements in packer and plug design, minimizing packer element extrusion. Based on these changes, operators now have more intervention options at reduced risk. While applicable to both new completions and interventions, this paper will focus on intervention technology.
For many years, extrusion gap has been controlled primarily by the use of a "Gauge Ring" as a packer back up. While successful, this approach dictates a large OD packer or plug to minimize extrusion gap. As our industry has developed more tortuous well bore geometry, large ODs have led to running and pulling problems. These designs have also prevented many operators from recovering failed zones. Water encroachment, gas migration and failed sand screens have often been dealt with by re-completion. Options were limited to inflatable systems, long elastomer or umbrella types of plugs. Horizontal completions further reduced that to only inflatable solutions, due to umbrella systems dependency on cement. Recent developments in high expansion products have opened up new opportunities to recover from these types of problems.
High expansion elastomers and new design packer back-up systems allow for actual V-Rated packer, plug and straddle systems. With this benefit, comes the added value of a retrievable system. Intervention work always carries with it the risk of failure. Recovery from a failed intervention can sometimes be a return to the original work-over plan. The most successful of the new systems incorporate expanding packer back-ups. High expansion types of systems are now being used for:
Horizontal sand control in failed screens
Packer failure recovery
Straddles, straddles with stand-alone screens
Zonal isolations, (including straddles)
This type of equipment allows for the recovery of a failed intervention, as well as recovery from a change in wellbore dynamics. If the intervention team set the high expansion style system in the wrong place, they simply recover that and re-run at the correct depth. Should wellbore changes dictate a change, all or part of that system can be recovered and modified to accommodate the change in pressure/gas/water/sand.
In conclusion, the ability to reduce extrusion gap, while at the same time reducing OD of completion / re-completion components, brings operators new avenues of success with reduced risk. Exciting new applications include, high expansion style straddles with sliding sleeves, Smart valves, and chemical injection systems.