Case Studies

P&A Application in Norway North Sea September 2017

Well Abandonment with Wel-lok™ STC

Identification of problem

A client required isolation in the uncemented annulus behind a 7 5/8” liner that was run inside 9 5/8” casing.

For proper well control, the client could not remove the 5 ½” tubing in the well which had a 4.276” ID mule shoe on the bottom and could not establish sufficient injection into the annulus to squeeze cement or resin. This required a tool with a maximum OD of 4.0” to set inside 7 5/8” liner and seal out to 9 5/8” casing through perforations without circulating or squeezing from surface.

Wel-lok™ STC was set in a perforated section of the 7 5/8” liner to isolate the wellbore out to the 9 5/8” casing.


This tool was qualified to 1,500 psi differential pressure in 7 5/8” x 9 5/8” casings at our testing facility in Houston, TX. For field deployment, the perforation guns used perforated both the 7 5/8” liner and the 9 5/8” casing. As a result, the Wel-lok™ STC did not achieve a positive pressure test in the field deployment as it was not designed or qualified to seal beyond the 9 5/8” casing.