When it comes to fires and saltwater disposal tanks, it’s not what the tank is made of, a Minot tank manufacturer says. It’s what’s inside the tank, and how it’s handled.
Shane Kunnanz, with Fiberglass Specialities in Minot, said he was prompted to research the matter more thoroughly after media articles reported questions about fiber glass tanks and their susceptibility to fires and lightning strikes.
McKenzie County has had four to five fires at saltwater disposals this year, all involving fiberglass tanks, according to McKenzie County Emergency Management Director Karolin Jappe. She has been pressing state officials to look into the management of saltwater tanks, which state regulators have said are likely to double or triple in the Bakken during the next decade.
Kunnanz has been making fiberglass tanks for the Oil Patch since 2008.
“Once a steel tank is coated to prevent corrosion (from salt water), they are the same as a fiberglass tank electrically,” Kunnanz said. “Both will have static electricity to deal with.”
He’s been working with Lightning Masters, a firm out of Florida that specializes in lightning and static electricity solutions for industrial facilities.
Why produced water is such a problem
Produced water in the Bakken is about 13 times saltier than the sea, and thus highly corrosive.
Steel tanks that are going to hold such material are generally coated to resist corrosion. But the coatings wear out and can fail, leading to spills. Many companies thus choose fiberglass. Not just because it is cheaper than a steel tank, but also because it doesn’t rust.
Produced water isn’t just salty, of course. It came up from the ground with oil and gas production, so also contains flammable materials. Inside a tank, the volatile chemicals in the brine vaporize, filling any available air space in the tank with flammable fumes.
When a truck driver comes to take some of the brine to a disposal well, the drawdown introduces air into the tank. This is adding oxygen into a flammable mixture.
During a drawdown, static electricity also begins to build up inside the tank. If this is not safely dissipated, it can generate a spark.
One spark, however tiny, is all it takes to light a saltwater tank up. In a fire, the lids of the tanks are supposed to fly off like frisbees. That’s in lieu of the entire tank taking off like a rocket ship.
Lightning is the X factor
A lightning strike poses two types of threats to a tank.
First, a lightning strike, even if it doesn’t hit a tank directly, can cause a sudden difference in electric potential. This, generally will lead to equalization. That is an electrical arc taking place in the air. It’s similar to what happens when you touch a metallic doorknob and a spark flies, but on a much larger scale.
The second issue is that lightning is super hot. We’re talking 50,000 degrees Fahrenheit hot. That kind heat by itself can instantly ignite any flammable material.
So in addition to structural materials that keep the lightning strike away from tanks and convey the energy to the ground, Bruce Kaiser, with Lightning Masters, recommends proper venting of the tanks.
“In the case of both an arc and a direct strike the presence of a flammable gas determines if there will be an ignition,” he said. “That is why proper venting of these (tank) batteries is essential. No gas, no fire. No boom. Ideally, the tanks should be vented into a vapor recovery unit, or at least through a manifold capped with a flame arrestor, not allowing any gas to be available for ignition.”
Kaiser is meanwhile working on a fire extinguisher that would screw into a tank. If the temperature gets high, it would go off, immediately putting the fire out, inside the tank.
In the meantime, he estimates that the full range of lightning and static prevention measures costs around $1,200 per tank. The tanks themselves vary in cost, but are generally in excess of $10,000 each.
A fire at one tank often leads to a fire at the rest, since they are connected and in close proximity. A seven-tank battery is thus in excess of a $70,000 investment.
He estimates that 30,000 tanks nationwide have some type of lightning protection.
“There’s a lot more than 30,000 tanks out there,” he said. “(Protecting an expensive tank) is common sense,” he said. “Which is obviously not all too common.”
Study, rules needed
Kunnanz said he is glad the state is studying the problem and believes it is needed.
Tanks stand 20 to 30 feet high, and are generally set down on a flat prairie. That makes them tall, attractive targets should a lightning storm roll through.
“Right now, there is zero requirement for companies to install lightning protection or static drains on their facilities,” Kunnanz said. “It is completely voluntary.”
His only concern with the study is that it be well-rounded, and look at all aspects of the problem, including such things as human error.
“I feel like human error is something that is always a problem,” Kunnanz said. “We need to come up with a way to ensure that people adhere to the policies that are in place.”
John Harju, with the Energy & Environmental Research Center, told the Williston Herald that a cursory look at available industry data do not show fundamental differences between fiberglass and steel tanks when it comes to holding saltwater.
But, he added, the center will interview those familiar with what is going on, as well as reviewing available studies, to get a better handle on the issues. That is assuming that the state approves a proposed $300,000 study of the issue. The proposal, from the Oil and Gas Research Council, is set to go before the North Dakota Industrial Commission for approval on Aug. 28.
“We just need to do our due diligence, so we can design whatever follow-on study needs to be done,” Harju said. “It’s important that we find quality data. That will be our primary objective.”