This was the first North Sea application of the company’s metal-to-metal downhole sealing solutions, which employ modified thermite heaters to reduce the heating time to form metal-to-metal seals from hours to minutes.
The systems are also said to eliminate the need for special wireline equipment, or restrictions on deployment depth, as they can be run on standard wireline.
With a wireline go-pin top connection, BiSN adds, the technology requires 240V and 60 mA for 15 seconds (conventional wireline-set tools) to activate the thermite chemical reaction heater.
During the abandonment phase of multiple wells at Valhall, standard zonal isolation led to surface tubing pressure issues. To resolve this, the company set a Wel-lok M2M TS tubing seal in the liner in order to isolate the producing zone.
The tool was set by activating the thermite chemical reaction heater, melting the bismuth alloy on the outside of the tool, thereby allowing it to fill the inside of the liner. When solidified, the alloy expanded, creating a gas tight seal in the liner and isolating the non-permeable zone.
After setting the tools in multiple wells, surface liner pressure was eliminated in each case.