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Environmental Science/What types of organic matter comprise oil?


I am an artist and I have been working on a complex drawing which begins with the protocell and moves out through evolution into more and more complex life forms. I was thinking about its purpose and meaning and thought it would be much more potent if what I am drawing is the lifeforms that are compressed over time and become oil. I have been doing some research online to find out if I can fit what I have draw so far into this concept, but I have been getting conflicting answers.
I have read that oil is made from single celled aquatic plants and animals, mainly from seas but sometimes from swamps as well.
I have drawn many more complex multi cellular plants and animals. Is is likely that bit and pieces of these animals fell to the bottom of the ocean as marine snow and were also compressed into petroleum?
What about land plants and animals. I know that coal is formed mainly from the woody parts of trees, but is it possible and pieces of trees or land animals ended up in swamps or in rivers and carried to the sea.
I have read conflicting things about the time period that oil is from. One website said that the plants and animals that comprise it are at least 300 million years old, where as another site said that it is 70% mesozoic era life forms.
As of right now I have draw up to the permian era. I have included Synapsid and Diapsid reptiles as well as beetles and flying insects, ginkgoales and conifers.
Is it wrong to assume bits and pieces of these lifeforms could also also contribute to the matter that turned into oil?
Thank you so much for your help!

The short answer to your complex question is Yes, you are right in your assumptions. The easiest answer to your question is found in the topic of pyrolysis, which is a process of applying heat to organic compounds to break them down, without combustion. Look up the term in Wikipedia.  Oil, as it is found in the ground is not really a quality control substance. Mother Nature doesn't work that way. The pyrolysis process discussed by Wikipedia may be at higher temperatures, which result in charcoal and carbon end products, plus the oils. In nature, the process generally occurs at lower temperatures, and so more oil exists, as tars and heavy ends.
Oil does contain lots of stuff derived from plants and animals, and the combination of temperature, pressure, and time transforms what was living organic materials into the stuff we call oil. Oil itself is a complex mixture of lots of organic compounds. Some oils are very heavy in carbon (such as Orinoco Crude Oil). That oil is almost pure carbon in suspension and I'm told it is like trying to burn No 6 or Residual Oils, because you have to heat it to over 180 F to even get it to flow so that you can pump it-- but it does have a lot of energy per pound, plus a lot of other compounds which generate pollution. West Texas Intermediate is one of the benchmark crude oils.( and it a light sweet crude which contains relatively more volatile components that other oils. (Look up Heavy Crude Oil on Wikipedia.)
The point is that what we see as oil and gasoline is a refined product which has been thermally separated into cuts or fractions. Gasoline is one of the lightest fractions. Tar and Asphalts are among the heaviest fractions. All are basically byproducts of pyrolysis of organic materials over time and at moderate pressures. In short, everything went into the swamp/pot (think stone soup), and got covered with mud, and more organics, and then buried and cooked under pressure, so yes, you can find lots of traces of all kinds of things in oils, and even some shells in the formations.
Hope that helps.

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David L. Russell, PE


I`m a Chemical,Civil and Environmental Engineer and have a number of projects in all phases of the environment. I have worked in the chemical industry and am active in professional societies, and am currently on an industrial wastes committee for the Water Environment Federation, and have taught courses in remediation in the US and abroad. I have written one book on Remediation of petroleum Contaminated Sites, and have a second book on PRACTICAL WASTEWATER TREATMENT to be published by John Wiley in September, 2006. I've also written over 30 articles on various elements of environmental problems and cleanup. Most Recently, I have addressed a NATO Scientific and Techical Conference on Ecoterrorism, and have worked with the same group on remediation of sites contaminated with Chemical Warfare Agent materials and othe materials as well. . I can answer q`s about Chemical and Environmental Engineering, land development, air pollution, water pollution, soil and water cleanup, combustion, international environmental problems, industrial processes chemical processes. Civil and Environmental and Chemical Engineering. Overall, I have over 35 years of experience in this area. Note: I do not answer homework questions


I love work in the third world and developing areas because it is challenging and one can get a sense of accomplishment.

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