Steve-
You asked about the components of crude oil. Think of it as a tree with the lightest hydrocarbons in the chain at the top.
The upper part of the tree with the lightest being hydrogen, followed by ethane, propane, butane, pentane, and hexane. These are light enough to be liquid only under pressure.
The center part of the tree would be gasoline, naptha, kerosene and diesel.
The bottom part of the tree would be gas oil and residuum.
The first pass in a refinery is through a "crude unit" where the oil is heated and sent through a series of towers known as fractionators. All of the above components are separated and sent to storage of some nature. Only some of the gasoline at this point is marketable, even after it has been passed through a sulfur treating system, mainly because they have to meet specifications and has to be further refined or blended to meet octane requirements.
From the upper part of the tree, the butanes, pentanes and hexanes can be processed through a reactor system and be converted to additional gasoline.
The middle of the tree with the naptha and kerosene is converted mainly into jet fuel with part of the naptha conversion also resulting in more gasoline.
The diesel that came from the first pass in the crude unit is marketable at this point after sulfur removal.
Now for the bottom of the tree... the gas oil and resid is passed through a series of systems that allow some 95% of this to be converted to more gasoline and diesel with the remaining 5% being the consistency of road tar. At this point there is nothing left from the original pass from the crude unit.
In addition to crude processing, there is processing of NGL (Natural Gas Liquids) and about 60% of this is refined into gasoline, with the remainder being propane and butane.
As you can see gasoline and diesel production is not a simple process. As far as the seasonal adjustments that are made within a refinery to either increase gasoline or diesel production, yes they can produce more or less of each item by adjusting the temperatures of the cat crackers, but there is only so much that can be extracted from a barrel of crude, be it gasoline or diesel. As far heating oil, it basically slightly heavier in composition than diesel and this is achieved by how the process is controlled.
There are almost as many different crude oils from all over the world as there are different species of fish in the sea. Each crude oil is different in composition, specific gravity and contain different amounts of gasoline and diesel.
I hope that I have not gone to far in depth on trying to explain what happens in a refinery and this sheds some light on how gasoline and diesel are produced. As far at the prices on the diesel, the single largest contributor to high prices will be the ULSD. It takes lots of equipment, energy, and time to meet the specifications that the Federal Govt. has imposed on the refining industry. True, demand will be an important factor in the cost of diesel and personally I think that diesel will continue to be more expensive than gasoline.
About Dave's link that relates to $40-50/bbl crude oil price, I think the author is being optimistic about the world crude oil situation. I would love to see it as it really hurts to fill up the F-250 after rolling down the road with the Montana attached.
Charlie
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