What products does oil yield?
November 10, 2005 11:59 AM   Subscribe

Where do I find information about the yield of different products from different sorts of crude oil?

I am looking for a source for yields of products from various types of crude. I am interested, for example, in knowing gas vs distillates for a few popular flavors of crude (wti, maya, brent, saudi etc). I have been poking around the EIA and the usual web sources but havent been able to get any hard data. Ideally, I would get some sense for how the yields have changed over time.
posted by shothotbot to Work & Money (16 answers total)
While people are answering that, I have a simpler question: converting barrels of oil to gasoline in the general case. I know the standard number is 42, but I believe that's merely a volume conversion, and doesn't take into account the process of refining. (shothotbot -- hope you don't mind my jumping onto your question).
posted by alms at 12:11 PM on November 10, 2005

alms, your question was discussed here within the last month or 2
posted by jacobsee at 12:44 PM on November 10, 2005

justkevin, do you know where diesel fuel would fall on your chart?
posted by jacobsee at 12:49 PM on November 10, 2005

thanks, what else falls in that category?
posted by jacobsee at 12:52 PM on November 10, 2005

I don't know a ready source of the data you're looking for. It's fairly closely held by the oil refiners as confidential commercial data.

What I can offer you are simulated distillation curves for all of the crude types you mention, which you could use to get the direct distillate fractions you're interested in. We've got about 200 or so SIMDIS analyses done for various crude types, so we'll probably have a good match to what you're looking for. I'll have to pull these numbers out of our database for you. Drop me a line at the mail in my profile with the crude types you're interested in and we can discuss it.

This isn't going to help you with reformed crude products, but will give you an idea of what's in the base oil. As I understand it anyway, what comes out of a refinery now is highly tunable anyway. If they need more gas, they make more gas at the expense of the gas oil distillates, or vice versa as the market demands.

On preview: that California graph is pretty, but, I think kind of meaningless. It's a pretty optimistic view of what you can get out of a raw barrel---I can tell you that they aren't getting that out of a barrel of Point Huemene API 11 stock, for instance.
posted by bonehead at 12:55 PM on November 10, 2005

Jacobsee: it's generally called Fuel #2. Road diesel is the major product, but home heating oil and some marine fuel are the other main products.
posted by bonehead at 12:56 PM on November 10, 2005

Actually, thinking about it, I bet that California Energy Comission graph is based on the US DOE refinery production data. You can find more detail on this page here. The raw data can be found here.
posted by bonehead at 1:02 PM on November 10, 2005

From a second-hand source (my dad worked in a refinery all his life) the difference in crude stocks isn't just the oil itself, but also the crap you want to remove from all the final products, like sulphur. I seem to recall that the only thing I ever heard mentioned about different sources of crude was sulphur content. Wikipedia seems to semi-support this. The othe rmajor different is viscosity/specific gravity.

Due to pollution controls, if you're going to burn the final product (fuel oil versus lubrication oil) you don't want any sulphur in it. Acid rain, etc.
posted by GuyZero at 1:24 PM on November 10, 2005

Wax (n-alkanes higher than C18), Resin, Asphaltene content are all significant as well.

Most refiners grade by a quantity called API gravity, which is a measure of specific gravity. Suphur content is probably the second most important quantity to a refiner. Pour point used to be quoted a lot too, but has fallen out of favour to some degree. Viscosity isn't important for crudes because of all the ammendments producers add to the oil (on the other hand, heavy fuels are sold by viscosity grade, e.g., IFO-180, IFO-300). Emulsion formation is importantant too, but only to know how much emulsion breakers are needed.
posted by bonehead at 2:06 PM on November 10, 2005

The graph linked to by justkevin implies that a barrel of crude oil produces more than three times as much gasoline as diesel. I understand from other posters that this proportion can be altered. However, if the California graph is an accurate depiction of the choices made by the refineries supplying gas stations in the United States, then in terms of the amount of crude oil needed, isn't buying a gallon of diesel effectively the same as buying three gallons of gasoline? And isn't it therefore incorrect to think that driving a car in the United States whose mpg on diesel is twice as good as a gasoline-powered car is actually reducing American crude oil consumption? (Note that "twice as good" is an exaggeration, at least if a VW Golf is representative.)

In other words, is driving a diesel car an effective way (in the short-term) for a consumer to affect the nation's crude oil consumption? Or should I go for the hybrid after all? (And why don't they make diesel hybrids?)

Sorry if this is a thread derail, but I've been wondering this for some time.
posted by obliquicity at 4:30 PM on November 10, 2005 [1 favorite]

If you Google on 'assay crude oil', you can find a decent number of crude assays on-line. The more common marker-type crudes you mention should show up, sometimes as samples for bigger services. The US Strategic Petroleum Reserve Assay Manual is on-line and explains some of what you are looking for, although the SPR consists of mixtures of individual crudes.

Bonehead is right on the actual yields of refined products. That depends entirely on the refinery that processes it. The assay will only tell you how it slices up when you process it via crude / vacuum distillation.

What an actual refinery can do with an actual crude oil is the commercially sensitive part. It helps them to decide which crudes to buy. They use some pretty sophisticated tools to weigh the trade-offs and decide the most profitable course.

Obliquicity - the fact that a barrel yields 3x as much gasoline as diesel is a function of the configuration of the refinery as well. Straight-run, the refinery might only yield 20% gasoline material. It's how much conversion a refinery can perform that matters. Conversion would convert heavier oil to lighter products.

There is a small matter of volume expansion in conversion refining, but it accounts for maybe 5% on a barrel of oil. It comes from, let's say, "restructuring" the molecules involved. Same atoms, but different molecules; you redistribute the mix of hydrogen and carbon into less dense, lighter materials. In the case of fluid catalytic cracking, for instance, you can make heavy oil into gasoline, but you will also make some of it into gas and some of it will be lost as coke. It's a trade-off, but a profitable one.

Diesel is a more efficient fuel for an equivalent volume; it has a higher calorific value (about 20% more than gasoline), which explains why you get more miles per gallon from it. Diesel is a more dense material (so, you get more weight per unit volume). Effectively, you get more carbon per gallon than gasoline. From a consumer's point of view, if they cost the same, diesel is a better deal. From an environmental point of view, I think your CO2 emissions would be about the same per mile driven.

The economics of refining probably suggest that you want to make more gasoline and less diesel; because of density differences, you can make more gallons of gasoline from a barrel of oil than you can diesel. Again, if they cost the same, why not make more gallons? Here it becomes a market problem.

Are hybrids a better answer? I don't know. They relocate the pollution from the tailpipe to the power plant. And they effectively turn coal or nuclear into transport fuels and reduce reliance on imported oil. Because of generating, transmission and storage losses, electricity for propulsion is presumably less efficient than fossil fuels. But if you sequester CO2 emissions (maybe coming in the future) you might have a better proposition for the environment. I guess the jury is still out on this. But it's neat.

As for why they don't make diesel hybrids, it's probably because a diesel engine is a different beast to a gasoline engine. Heavier. More efficient when it runs hot. Harder to switch over efficiently mid-stream.
posted by sagwalla at 6:04 AM on November 11, 2005 [1 favorite]

Here's a page with some links to assays of Brent, WTI and Maya.
posted by sagwalla at 6:42 AM on November 11, 2005

As for why they don't make diesel hybrids...

Diesel engines also don't like to be stopped and started repeatedly, which limits their usability in a full hybrid system.
posted by alms at 7:51 AM on November 11, 2005

sagwalla's post remind me of the other major source for data: the Oil and Gas journal. The pdf's on the pages he links to are photocopies of the data pages OGJ periodically publishes.
posted by bonehead at 8:39 AM on November 11, 2005

Are hybrids a better answer? I don't know. They relocate the pollution from the tailpipe to the power plant.

Aren't most common hybrids these days self contained? In other words they charge their batteries from the engine and from regenerative braking, and not by plugging them in?

If so, this means they are simply more efficient overall and hence do reduce overall pollution. This ignores the possibility that a hybrid owner will drive more as driving becomes cheaper.
posted by jacobsee at 9:13 AM on November 11, 2005

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