Case Studies

Repairing a production casing leak for a Canadian operator

Intervention with Wel-lok™ CLS (Casing Leak Seal) Tool

A Canadian operator had a well with a leak in the 7″ production casing. The leak zone had good cement behind the production casing but was unable to hold pressure, losing more than 250 PSI over 10 minutes.

Seal leak in situ while maintaining full drift diameter:

The customer desired a solution that would seal the casing leak without restricting drift access to zones deeper in the well. A tool was needed that could seal into the leak and then be milled to provide this full-bore access without damaging the seal.

A BiSN Wel-lok™ CLS (Casing Lead Seal) Tool was deployed in the well to the depth of the casing leak. The thermite heater was activated, melting the bismuth alloy. The low viscosity, liquid bismuth alloy flows like water, and was able to completely fill the leak path. While the alloy was still molten, the thermite heater was removed, leaving a solid bismuth alloy plug. The bismuth alloy then solidified, sealing off the casing leak. The thermite heater was retrieved to surface.


The operator then successfully pressure tested the plug, verifying that it was set and covering the casing leak. They then ran in hole with a mill and milled through the entirety of the bismuth alloy plug, reopening the well to full drift diameter and providing access to the deeper zones of the well. After completing the milling process, the customer performed successful 1000 PSI and 1500 PSI pressure tests, showing that the bismuth alloy had repaired the casing leak.

  • Casing leak repaired successfully in situ
  • Internal plug milled out, allowing full drift diameter access
  • Seal passed pressure test of 1500 PSI differential
  • Significantly reduced casing leak repair time for operator

BiSN provided the customer with a reliable, permanent repair to the leaking production casing. This leak repair was completed in the well while still providing full drift access to the customer. BiSN was able to help the operator reduce HSE risks, operation time, and cost.

Are you looking for a cost-effective and sustainable solution for your business? Contact our technical team today.