The concept of used an expandable pleated ring to achieve a seal in a wellbore was originally conceived for application as a high temperature packer or bridge plug for thermal heavy oil recovery operations. It starts as a round steel ring which is mechanically bent or pleated to reduce is external diameter. Once in location in the wellbore, it is compressed and returned to its original size exerting a powerful external force on the inside of the casing. This results in expansion and a seal.
Cutaway of expanded tool after removal of PMA, at right.
The Polymer-Modified Asphalt Tool (PMAT) incorporates multiple pleated rings. As a sealing agent, the tool uses Polymer-Modified Asphalt (PMA), a powerful sealant that does not shrink and is impervious to water or other wellbore liquids. The PMA resides within the PMAT while running in the well. When the PMAT is expanded, the PMA extrudes in all directions including above and below the plug. This prevents corrosion of the rings, the casing where the plug is set, and above and below the plug.
A cement plug above a bridge plug will in too many instances leak over time. Winterhawk is of the view its PMAT plug will outlast the casing.
PMAT setting can also seal the outside of the casing as well as the inside. Depending upon the expanded diameter of the rings, the PMAT can provide small to significant expansion of the casing. This can provide an extra level of sealing integrity of the cement to shut off existing annular leakage or prevent future annular leakage.
Tool after PMA coating, at right.
Existing bridge plugs with cement provide sealing to the annulus of the casing between the casing and wellbore.