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Downhole Sealing Solution Found In Unique Bismuth Based Alloy

A technology using bismuth based alloys may help a festering problem with abandoned wells in Western Canada.

The federal government announced a $1.7 billion commitment toward the clean-up of abandoned and orphan wells in Alberta, Saskatchewan and B.C. last year. These wells are considered a concern because many are presently leaking methane due to ineffective abandonment programs.

A company named BiSN is creating gas-tight metal-to-metal seals using patented modified thermite heaters to melt bismuth-based alloys downhole.

“The best way to think about our tool is as a large candle,” said Paul Carragher, who founded BiSN in 2010 and is the company’s CEO, of the Wel-lok M2M technology, during a webinar posted on the company’s website.

“You’ve got the alloy on the outside, which is your wax and you’ve got your thermite heater on the inside which is your wick.”

“When that thermite heater burns it will burn top to bottom just like a candle does.”

With its new technology, the company is “fundamentally changing the way downhole sealing is carried out,” he said, breaking the mould of traditional
methods and “changing the way operators look at well abandonment.”

One of the functions of Wel-lok M2M technology, which is used in a range of tools and applications, is to provide a permanent seal in well abandonment.

“BiSN and our theoretically-tested 3,000-year bismuth alloy barrier provides the Canadian oil and gas industry with an economically competitive alternative to traditional plugs and remediation techniques,” says Steve Petten, BiSN Canadian general manager. “However, we believe the true value of our technology is in the safety and environmental benefits we offer our customers today and in the future.”

This qualified 3,000-year-barrier is expected to limit the need to re-enter wells in the future.

“We are taking bismuth alloy in a solid form downhole, melting and sealing off wellbore issues; whether those are surface vent flow, shutting off nonproductive perforations, sealing leaks in tubing and completions equipment, and this is all done with a wireline or slickline deployed tool,” he adds.

There are more than 90,000 inactive wells and more than 70,000 abandoned wells in Alberta, says the provincial government. Cement and bridge plugs are the conventional methods for abandonment operations.

“We think this will reduce the number of re-entries that industry will have to do here of cement jobs that have been pumped that appear to fix the wells and then five years later they have gas coming to surface again because the cement has deteriorated,” says Petten.

“This is a stronger material than cement,” he adds. “It’s basically giving a metal-to-metal barrier here.”

Bismuth expands 3.8 per cent as it solidi􀁷es, forcing possible trapped gas out of the annulus and stopping any further migration from the lower gas source.

Wel-lok M2M offers the benefit of gas-tight-barriers without needing to pump from the surface. The alloy’s high degree of density allows it to flow into the well with gravity alone.

“There’s an ease of business,” says Petten of the advantage to the technology, also singling out the advantage of running less heavy equipment down the road. “It’s one guy, one tool.”

This method also cuts down on the time required for the operation. Melting and solidifying the bismuth barrier takes minutes downhole and can be pressure-tested within an hour, Petten says. In comparison, concrete takes about 24 hours to cure.

Wel-lok M2M tools may be used in applications including the reduction of water production in existing wells, eliminating gas migration in cemented annuli, repairing a leaking production packer, sealing perforations in cased hole completions and reducing unwanted sand production, among others.

BiSN also has a product that runs its bismuth alloy on the outside of the casing when the user is drilling a well. The company deploys its thermite heater in the casing to melt the alloy, sealing any micro-annulus that may have formed during drilling and completion of the well.

Nearly 200 of its tools have been field deployed to date. Fourty-eight per cent of these deployments have been for plug and abandonment purposes. BiSN has manufacturing facilities in the United Kingdom and Houston, Texas.