The (not so) explosive science behind oil sands corrosion
At CanmetENERGY near Devon, Heather Dettman cools a hotly contested debate
Heather Dettman is only interested in the facts. She’s a research scientist and is not about to wade into any politically charged debate about the relative safety of transporting different grades of crude oil in pipelines. Leave that to the environmentalists, journalists and talking heads on network news shows. “You never know how any idea will be used,” says Dettman, who has been working out of the Devon Research Centre southwest of Edmonton since 1996. She works in CanmetENERGY’s mini refinery there, testing oil sands crude and advising industry on what refining processes are most efficient.
It’s pretty run-of-the-mill work. But her research into the corrosivity levels of crude oil – particularly oil sands and diluted bitumen – has assumed new significance of late. It’s played an unlikely role in a modern-day drama pitting activists and environmentalists against pipeline operators and the products they transport.
It turns out oil sands crude is not the acidic bogeyman described by the Natural Resources Defense Council. Using a miniature corrosion test unit in her lab, Dettman found that crude oil only becomes acutely corrosive when it reaches temperatures between 220 and 400 degrees Celsius, when the molecules are broken down into their base forms. That breakdown of molecules activates smaller molecules like hydrogen sulfide, a substance capable of corroding heavy metals.
“It proves the point that I was suggesting,” Dettman says. That is, corrosion caused by crude oil is minimal below those temperatures. “When it’s just in the pipeline, it’s very, very diluted,” the researcher says. The acidic component of the oil only becomes active in the vacuum distillation phase of the refining process, long after it has been transported via pipeline.
Dettman didn’t see herself working in the oil and gas sector after university. She wound up in Ottawa after graduating from the University of Alberta with a PhD in biochemistry and soon found herself immersed in the oil industry. She didn’t exactly find the work glamorous. When she first started, she remembers wondering why the oil had to be black.
Today, Dettman embraces her work with a sort of scientific gusto. She’s published a number of reports on the acid levels in crude oil, and has presented her findings to many different audiences. Her most recent report is entitled: The Influence of Naphthenic Acid and Sulphur Compound Structure on Global Crude Corrosivity Under Vacuum Distillation Conditions.
In the U.S., the perceived corrosive properties of diluted bitumen emerged as a rallying cry for opponents of TransCanada Corp.’s Keystone XL expansion. Many claimed the corrosive nature of oil sands crude made the resource too volatile to ship down hundreds of kilometers of pipeline.
Dettman’s findings flow in the opposite direction. She concedes, though, that no single researcher or producer can have an absolute understanding of how the chemical makeup of unconventional oil fits into broader development methods. The industry is too complex and has too many components.
But Dettman’s understanding of the industry runs deeper than most. She fears the biggest loser amid the charged oil sands rhetoric coming from either side of the debate is science. “It’s confusing for everybody,” she says. “Even in the industry it can be confusing because you need to have so many areas of expertise to really make the petroleum industry work. You need to have the people who understand the temperature and pressure, and then people understanding the metallurgy and people understanding the molecules and the products. There are so many aspects.”
For all the talk of emerging technologies in the oil and gas sector, the method for testing acid levels in crude oil is old hat. The test used today was developed in 1956. Called the American Standard Test Method, it’s considered the most dependable process in the industry. The oil is titrated – or neutralized in order to reveal its chemical makeup – for molecules like sulfur, and given a total acid number (TAN). Dettman’s most recent report argues that corrosion is not caused by high concentrations of acidic molecules, but by the size of those molecules – when they’re broken down into their base forms. “The assumption in the industry is that if it’s a high TAN it’s going to be very corrosive, and they even de-value the oil based on its TAN value. So, oil is penalized for having a high acid number.”
Not only does the oil itself differ largely from other sources, the methods that test those differences range dramatically. “Our oils are less corrosive than other international oils have been found to be,” Dettman says. “We’d like to actually develop a method to prove it, to be able to compare them properly and demonstrate it.”
It’s impossible to say how long that might take. Opinions differ within the industry on how best to deal with corrosion. “Everybody’s just looking at their own part of the picture. Throughout my career that’s been an ongoing issue. So the idea is to help educate everybody, so at least they can appreciate what the other argument is. In the end, what research is about is learning what you can about systems and getting publications out.”
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