Study of oil from deadly derailment points to Bakken crude’s volatility
WILLISTON, N.D. – On July 6 last year, a train carrying crude oil from North Dakota to a refinery in eastern Canada was left parked on a hillside in Quebec. It rolled backward down the hill, derailing and crashing into a small town, with railcars bursting into flames, killing 47 people.
While investigators pointed early on to the train’s brakes, the violent explosions prompted Canadian officials to question the volatility of the Bakken crude.
The crude oil that train carried had volatility similar to gasoline, said Sylvie Dionne, author of the Transportation Safety Board of Canada’s laboratory report published last month on samples taken from the train.
The oil had a low flash point, which indicates it would ignite at low temperatures, and a high vapor pressure, which indicates how readily the oil would ignite at the temperature that was prevailing at the time of the derailment, Dionne said.
“Those two conditions together explain why it caught fire so easily,” said Dionne, manager for materials analysis and structures at the TSB. “The large amounts of it, because there were many tank cars and some of them released product, that explains why the fireball is so large.”
Other factors that contributed to the fireball were the rapid rate of release and the oil’s low viscosity, the report found.
The crude oil tested also had a low boiling point, the report said. The low flash point, low boiling point and high vapor pressure suggest the samples contained very light hydrocarbons, the report said.
“The lighter the hydrocarbons that are present in the crude, the more volatile it’s going to be,” Dionne said.
Questions about the volatility of the Bakken crude would come up again with other explosive derailments, including the one near Casselton on Dec. 30.
“We had no idea it was this volatile,” Casselton Fire Chief Tim McClean said in an interview last month, the same day he testified to a congressional committee about responding to the fiery derailment.
A federal study and a study commissioned by the North Dakota Petroleum Council are underway to analyze the characteristics of Bakken crude, but the results are not yet available.
“Bakken crude is comparable to other light sweet crudes according to all the information we have to date, but we know that some have questioned whether it is somehow different,” said Kari Cutting, vice president for the NDPC. “This study will provide a thorough third-party analysis to help regulators and industry determine the facts so we can make decisions based on sound science.”
The Canadian report may underestimate the volatility of the crude oil because some of the light hydrocarbons may have evaporated, Dionne said.
The engineering laboratory report analyzed samples from nine non-derailed tank at the end of the train and two tank cars from a different unit train that was transporting crude oil from the same origin in the Bakken.
Other findings include:
- There were multiple sources of ignition at the derailment site, such as damaged power lines.
- The Bakken crude analyzed had characteristics similar to other light, sweet crude oils.
- There was no indication that chemicals used in hydraulic fracturing affected the crude oil.
- The crude had a low sulfur content. Portable detectors used to measure hydrogen sulfide gas during the response did not detect the gas, which is extremely flammable and toxic.
While the report tests many characteristics of the Bakken crude, its scope was limited to the derailment and the Lac-Megantic investigation.
“It’s only applicable to the Bakken crude that was on that train,” Dionne said.
The Transportation Safety Board’s final investigative report on the derailment is still pending.
The North Dakota Petroleum Council recently announced it is doing its own study, a Bakken quality assurance study to help ensure public safety and consistent product quality.
The industry group is working with Dallas-based consultant Turner, Mason & Company and an independent commercial laboratory to study the range and variability of Bakken crude oil qualities.
“There’s a lot of independent sampling going on right now,” said Ron Ness, president of the North Dakota Petroleum Council. “You need to do it across the entire specific areas of the Bakken, so it’s not just a point A or point B.”
The consultant will take multiple samples from 12 locations and six rail depots in North Dakota and Montana, including samples from newer wells and more mature wells.
“We haven’t done this particular type of study and I don’t know that anybody has to be honest with you,” John Auers, executive vice president of Turner, Mason and Co. and head of the study, said in a recent interview.
A progress report on the study will be given in May at the Williston Basin Petroleum Conference, and results of the study will be shared with PHMSA and the American Petroleum Institute.
“This whole issue of rail and crude has brought that out,” Auers said. “In reality, Bakken isn’t a whole lot different than a lot of other light crudes.”
Days after the train carrying Bakken crude derailed and exploded near Casselton, the federal Pipeline and Hazardous Materials Safety Administration issued a safety alert indicating that Bakken crude may be more flammable than other types of oil.
Inspectors from PHMSA and the Federal Railroad Administration have been examining the chemical properties of Bakken crude through unannounced spot inspections and data collections.
Based on preliminary findings, PHMSA and FRA expanded the investigation to include bottom sediment and water, true vapor pressure, hydrogen sulfide, concentration limits of flammability and corrosiveness to steel and aluminum.
The results have not yet been released.
PHMSA issued an emergency order that requires crude oil shipments to be designated as Packing Group I or II, requiring the oil to be shipped in stronger rail cars.
PHMSA has proposed $93,000 in fines against three companies the agency says failed to properly classify Bakken crude. The agency’s legal counsel is reviewing responses from the three companies, a PHMSA spokesman said.
In January, the National Transportation Safety Board, which investigated the Casselton derailment, issued recommendations to PHMSA and the FRA.
One recommendation would require trying to avoid shipping hazardous materials though populated and sensitive areas. A second recommendation is to ensure rail carriers can handle the worst-case scenarios of a hazardous materials accident. A third recommendation called for checking on shippers and rail carriers to ensure they are properly classifying hazardous materials and have adequate safety and security plans.
"If unit trains of flammable liquids are going to be part of our nation's energy future, we need to make sure the hazardous materials classification is accurate, the route is well planned, and the tank cars are as robust as possible," NTSB chairwoman Deborah Hersman said at the time.
Sen. Heidi Heitkamp, D-N.D., said it’s important to get the results of the PHMSA study to inform regulations. While many are now saying that Bakken crude is more flammable, Heitkamp said she wants to see the results of the study.
“I suspect that might be true, but until I see test results, I’m going to withhold judgment,” she said.
Heitkamp said she wants the PHMSA study to be thorough, but hopes to see results within weeks.
“We need to move forward on regulation,” she said.