“Do you understand how sedimentary rock is formed and why it is different from igneous rock?”
I had a graduate level course in historical geology (although I was an undergrad at the time) from Prof Loudon, U. of Wis.-Madison, and a course in glacial geology (same institution), and hold a doctorate in soil science.
But I do not know how petroleum is formed, and do not know whether anyone does, there not having been any witnesses to the phenomenon in action, but surely the inquiring mind of curious man has conjured theories as to how this might have occurred, and written books and learned essays about their conclusions.
No one here knows? Very well, there’s always Google.
Thanks. I've had some of these type conversations on FR with people that argued that the depth alone proved it wasn't laid down by material from the surface.
We know we can produce oil directly from algae. When algae is trapped in sediment along with diatoms, plankton, etc, it doesn't have the oxygen source to decompose. Heat and pressure and a lot of time takes other more complex organic molecules like amino acids into crude oil. Keep in mind that crude oil is not a couple molecular structures but a vast array of hydrocarbons varying greatly from field to field and quite a mixture within each field.
The most common organic-rich sedimentary rock is black shale, deposited on an ancient ocean bottom. Temperature is the most important factor in turning organic matter into oil. The min temp for the formation of oil (~150°F) occurs typically at 7,000 ft. Oil is generated from that point down to about 300°F. If the source rock is deeper where temperatures exceed 300°F the breakdown will continue into the smaller, less complex hydrocarbons of natural gas.
As you have an understanding of geology, I would recommend the following book: