Open-hole Bismuth Straddle for Zonal Isolation of an Offset CO₂ Injection Well

The client did not originally know the extent of the corrosion damage to the 5-1/2” casing. After a successful logging campaign revealed the casing across the target formation had corroded completely, a unique open-hole solution had to be developed. With the open-hole diameter ranging from 5-1/2” to 9”, BiSN proposed a single heater configuration which could successfully be set across the size range. Alloy shot quantity could be adjusted to facilitate precise plug lengths in the different diameters in the field.

BiSN produced two 4.5” STC heaters which could seal various open-hole diameters that could be encountered. The lower plug utilized a timer activated running tool to successfully melt 400kg of alloy in an 8.5” open-hole, while the upper plug was used to melt 300kg of alloy in a 6.25” open-hole.

During both operations, the bare heater was run to depth before shot was dropped from surface down the work-string. After exiting through a ported sub, the shot accumulated around the heater until the thermite reaction was initiated. While the alloy was molten, the heater was removed to create a single material barrier in the harsh corrosive environment. A cement plug was spotted between the two alloy plugs to ensure proper space-out of the upper seal. A tag was conducted after each run to confirm the calculated plug height and after the final operation a successful inflow test was performed to verify the work had been successful.

BiSN’s Wel-Lok™ Seal Through Casing Tool (STC) was successfully used to create an open-hole straddle in this novel application.

• First ever use of BiSN technology for an open-hole straddle application.
• Superior corrosion resistance in CO₂ than any other barrier material.
• Flexibility to adjust alloy barrier height in the field for different open-hole diameters.

BiSN developed a novel straddle approach to remediate a complicated barrier restoration. The corrosive properties of CO₂ had eliminated sections of the wellbore so it was imperative that the remediation utilized a barrier material that could survive these harsh conditions, while still having the flexibility to set in various sizes of the open-hole. BiSN was able to help the operator reduce HSE risks, costs, and the challenge of returning to this troublesome well in the future.