Friday, January 3, 2014

Crude oil is probably flammable

Thanks to my morning Wonkbook e-mail, I see that there is concern that crude oil from the Bakken shale is more explosive than normal for crude oil:
After three fiery accidents involving trains carrying crude oil out of North Dakota's Bakken Shale, regulators and industry officials are trying to figure out why the oil is exploding. Crude is flammable, but before being refined into products such as gasoline it is rarely implicated in explosions. 
Yet earlier this week, when a BNSF Railway Co. train hauling 104 tank cars filled with Bakken crude struck another train, some of the cars exploded one after the other, releasing fireballs that blazed several stories above the frozen prairie. "Crude oil doesn't explode like that," said Matthew Goitia, chief executive of Peaker Energy Group LLC, a Houston company that is developing crude-by-rail terminals....
Of course, there are nasty chemicals to blame for this!:
...The energy industry has been reluctant to discuss publicly what might be causing the problem. It is possible, experts say, that unusually large amounts of naturally occurring and highly flammable petroleum products such as propane and ethane are coming out of the ground with the Bakken crude. Last March, Tesoro Logistics LP reported the Bakken crude it was transporting by rail was increasingly volatile. The San Antonio company didn't respond to a request for comment. 
Another possibility is that impurities are being introduced during hydraulic fracturing, or fracking. That process involves pumping chemicals or other additives along with water and sand into a well to free more fossil fuels. One such additive is hydrochloric acid, a highly caustic material, which federal investigators suspect could be corroding the inside of rail tank cars, weakening them. 
Oil from fracked wells can also be laced with benzene and other volatile and highly flammable organic compounds.
Laced! With benzene! What's this? The aromatics range of crude oil can be anywhere from 3 to 30%? Nuh-uh!

If I had to hazard a guess, I'd go with the first explanation, which is that crude that is fracked probably carries with it a higher percentage of trapped volatiles that are more flammable. I could be convinced that corrosion might play a role in this, but I'd be much likelier to believe that old/busted tank cars are being pressed into service inappropriately rather than an explanation about fracking fluid contamination. Interesting issue -- I'll try to keep an eye on this. 

9 comments:

  1. It'll be so much better when these sheeple wake up and realize we don't have to use flammable chemicals for fuel. We can use inflammable natural substances instead!

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    1. 'Inflammable' means flammable? What a country.

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  2. I hear that the companies building tanker cars can't keep up with demand. I wouldn't doubt that declines in quality control and/or maintenance/inspection are at least partially responsible for the catastrophic failures.

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  3. Do the people proposing HCl corrosion as a contributing factor realize that oil specifications include a maximum water content (typically <= 0.5% BS&W, but for rail might be a bit higher)? I have a hard time believing that any fracking additive is a) in high enough concentrations in the separated produced fluid to be of relevance, or b) would affect the crude to make it more explosive. There's always a spike in frack fluid returns shortly after completion, but that tapers off rather quickly once the near-wellbore volume has been turned over.

    As you say, this is probably the result of a more highly volatile crude. I would suspect it's producers shipping crude that hasn't been properly processed (degassed), whether for economic reasons (no facilities) or because they're unfamiliar with best practices for one of either the gas or the oil. You'd be surprised at how many producers are only familiar with one or the other.

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  4. Is it possible that this crude has been diluted for transport? Oil sands oil is too viscous to be transported by itself, so diluents are added, in the form of low molecular weight hydrocarbons. Where as regular crude may have a average MW of 100 (making this up for easy math), a more viscous crude from an unconventional oil play may have an average MW of say, 150, and to get the viscosity down, it would be mixed 1:1 with average MW 50 hydrocarbons.(for example, natural gas liquids) As a result, while a standard crude, say WTI (west texas intermediate) would have a relatively gaussian distribution of molecular weights centered around 100, diluted crude would be bimodal at 150 and 50. This results in a percentage by weight of the bulk that is higher in low MW, lower flashpoint, more volatile hydrocarbons, than normal, and these lower molecular weight hydrocarbons contribute to the increased flammability of the crude.

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  5. http://www.railwayage.com/index.php/regulatory/controversy-surrounds-lac-megantic-crude-oil-test-data.html

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  6. Could you help wit this please?
    Is there a point at which crude oil will be regarded non-flammable depending on water concentration or levels or any other factors in it?

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    1. I am not an oil/gas chemist, but I suspect that the basic question of "is this crude oil flammable?" depends on its contents. I doubt there is water in crude oil that is shipped, but I could be wrong. If it is typical crude oil, it's not very flammable (there's actually a definition of flammability, based on a measurement of its flashpoint. If it is high enough, it's considered "combustible" instead, I think.)

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    2. Thanks for the response, was just working on the flammability of crude oil as it comes from the well before separation processes.

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