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Geology/Gasoline as an oil by-product


I recently saw a presentation on oil and gas which stated that gasoline is a necessary by-product of of all oil products.  Apparently nowhere in all the various distillation charts is gasoline not by default it seems chemically impossible to not get gasoline when turning oil into any product.  In other words, even if all that oil was used for was plastic, there would still be a necessary by product amount of gasoline produced, which would need to be used up in combustion vehicles like cars, rather than burned off or buried.  Which means we will never get away from the use of gasoline as long as oil is drilled for and made into any of a multitude of products.  Is this understanding of oil and gas correct?

Hi Mike,
Interesting question, and the simple answer to the " ...we will never get away from the use of gasoline as long as oil is drilled..." part is no. But science seldom likes a simple answer so there might be a "yes" component.

First a quick background in petroleum geology.  We don't fully understand how petroleum forms but we do know it has an organic origin, and heat has a part in it's formation.  We know it's derived from sea life (phytoplankton mostly, but on land it's mostly woody stuff, so coal is formed there), that rains down to the sea bottom and is eventually covered over by sediment.  

Before the organics turn to petroleum they form a product called kerogen, which in turn changes to bitumen.  If you continue to add heat, some microbial action (we think), and some probable mineral catalysts the bitumen converts to a tar-like asphalt.  If you continue that process the asphalt breaks down into heavy oils first and then light oils.  If the temperature remains above 100 C some gases will come out.

The important thing here is that the process is continuous and can be interrupted at any point by natural occurrences or drilling.  So we can be processing anything from tar to natural gas.  When petroleum is sent to refineries it is processed into a lot of different items; and here's the yes/no.   Refineries "crack" the petroleum into materials of different weights according to their purpose.   But they can't just manufacture gasoline.  Early in the process only heavy oils are produced.  As it continues, lighter weight fractions will come out.

If refineries are producing heavier products, such as tar, asphalt, fuel oils, and some lubricants, they may never reach the conditions that generate gasoline so it will not be produced.   

However, we use a LOT of things that require lighter weight oils or gases, and that means gasoline will be a fraction of the product.   The US Energy Information Administration (EIA) says, in the US in 2010, about 2.7% of total petroleum consumption was used to make plastics.  That's about 191 million bbls LPG (liquid petroleum gas) and NGL (natural gas liquids).  We also used about 1.7% of total natural gas in US, 412 Bcf.  We also use the lighter fractions in medications, agriculture, and other applications.  So here, gasoline will be produced.

So.....yes/no.  We don't always have to produce gasoline during every procedure.  But, as long as petroleum products are being used, for the majority of applications, we probably will be producing gasoline; at least to some extent.  

Hope this helps.



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C. Robert Reszka, Jr.


I can answer any general geology question (rocks, minerals, stratigraphy, geomorphology etc.). My expertise is in the geology of the Michigan Basin, PreCambrian, Paleozoic and Recent. I can answer questions concerning mining and petroleum exploration and production and the laws concerning those activities. I can also answer questions concerning stratigraphy of the Michigan Basin. I will also answer questions about mineral and rock collecting in the Basin. I won`t be able to answer many specific questions on hydrology, geophysics or geochemistry. I may be able to answer very general questions in those venues.


I have been working for the State of Michigan for 36 years as a Geologist and a Resource Analyst. I have experience with Subsurface Geology and Petroleum Geology, mining in Michigan, and Sand Dune Mining and Protection issues.

Michigan Basin Geological Society

Decade of North American Geology.
Bedrock Geology of Michigan

BS Wayne State University

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