Eliminating Gas Migration in Cemented Annuli

Identification of problem:

The Wel-lok CRT™ (Cement Repair Tool) tool was developed to eliminate sustained casing pressure (Bradenhead pressure) in cemented annuli. Unlike traditional methods, this tool does not require and surface pumping pressure to squeeze or circulate the sealing material into place. The seal created is cost-effective and gas tight, saving the operator money and reducing their long-term liability.

Issues to overcome

An operator in the DJ Basin, Colorado, encountered bradenhead pressure in a well during well abandonment. Their first attempt to address this was to use a traditional method of section milling and spotting cement. Due to the unconsolidated formation, the section milled window washed out to ~15”, based on the volume of cement that was circulated and tagged TOC. Following the cement job, Bradenhead pressure continued to be seen at surface up to 1,500 psi as gas leaked past the porous cement plug.

Application

To solve this, the operator employed a “perf-wash-bismuth” solution for this well. The 7” production casing was perforated over a 6’ interval to break the existing cement behind the casing and create flow paths for the bismuth alloy to flow. A light washing was done over the perforated interval to clean out some of the cement residue followed by setting a Wel-lok™ CRT across the perforations. The well is now under a 1-month abatement period to allow all the trapped gas to be bled off above the BiSN plug before completing the well abandonment.