Case study: BiSN provides permanent, gas-tight seal for well experiencing gas migration

April 18, 2023
The company has eclipsed its own record for the largest bismuth plug with a recent offshore rigless deployment in the Gulf of Mexico.

HOUSTON  BiSN, a supplier of downhole sealing solutions and technology to the oil and gas industry, has eclipsed its own record for the largest bismuth plug with a recent deployment in the Gulf of Mexico.

A permanent, gas-tight seal was required for a well with a 36” OD that was experiencing gas migration.  In previous campaigns with Aker BP in Norway, BiSN had set the record for permanently sealing a 30” OD well in the North Sea. 

To seal a well of this size, BiSN scaled its Wel-lok technology and operations to meet the needs of both the size of the tool and the production timeline requested by the operator. With potential environmental damage to be considered, it was essential to meet the timeline required by the operator. The Wel-lok tool required more than 10,00 0kg of bismuth alloy and 2,200 kg of thermite, bringing the total weight to more than 20,000 kg.

Offshore rigless deployment

As the well had already been sealed using cement but was still experiencing gas migration, it was essential that BiSN deployed Wel-lok technology without using a rig and to avoid any potential environmental damage. A deployment method was applied using a liftboat and ROV to guide the tool into place to be fired.

Once the tool was activated by timer, the bismuth alloy flowed, filling and sealing the cross section of the conductor pipe in under an hour. Upon solidification, the alloy expanded creating a mechanical gas tight seal. The company said the burn time took about 55 minutes, resulting in significant environmental benefits and cost savings for the operator. ROVs continued to observe the well for 20 hours with no evidence of further gas migration.

CEO Paul Carragher said, “By utilizing BiSN’s technology, we ensured a permanent seal giving the supermajor operator peace of mind, saving them time as we were able to deploy from a liftboat and costs as a rig wasn’t necessary. We have now completed over 400 deployments worldwide with BiSN’s Wel-lok technology gaining significant momentum.”

BiSN said it continues to refine and develop Wel-lok technology for a variety of well intervention, completion, and plug and abandonment applications. Currently, Wel-lok technology has been commercially applied to 11 different applications, including water shutoff, cement repair, packer repair, and plug and abandonment.