Did oil come from Dinosaurs?

Question

Oil (and other carbon based fuels like Coal, but for this question, I'm more interested in Oil) is widely regarded as a "Fossil Fuel" because its origin was ancient flora and fauna, buried deep below the surface for millions of years while being transformed into oil.

Is this really the case?

Was there enough ancient plant and animal life trapped beneath the surface to account for known oil reserves?

People often say they are "filling their tank with dinosaurs" -- how much oil actually comes from dinosaurs or other animals versus other sources? A commenter asked for references for this claim, I thought the dinosaur gas tank connection was well known, here are a few references to dinosaurs in the gas tank:

• Chevron Dinosaur ad
• Just a Few Dinosaurs Short of a Full Tank
• Dinosaur Fossil Fuels T-shirt
• What's a dinosaur doing in my gas tank?
• Put another dinosaur in the gas tank

How did this ancient life come to be buried thousands of feet below the current surface of the earth and oceans? Continental drift and other plate tectonics shifting?

Was this transformation process 100% complete? Are there any cases where ancient plant matter, fossils, etc were pumped to the surface from an oil well?

Answer 1

Fossil fuels are fuels formed by natural processes such as anaerobic decomposition of buried dead organisms including phytoplankton and zooplankton that settled to the sea (or lake) bottom in large quantities under anoxic conditions. (Giant Oil and Gas Fields of the Decade, 1990–1999, Tulsa, Okla.: American Association of Petroleum Geologists, p.50) The age of the organisms and their resulting fossil fuels is typically millions of years, and sometimes exceeds 650 million years.

Over geological time, this organic matter, mixed with mud, got buried under heavy layers of sediment. The resulting high levels of heat and pressure caused the organic matter to chemically alter, first into a waxy material known as kerogen which is found in oil shales, and then with more heat into liquid and gaseous hydrocarbons in a process known as catagenesis. -source

I would not expect plant material to be found included in the oil. The organic material is compressed into kerogen during the formation process... oil is formed from that material (which is, in turn, imbeded in rock). As it turns into oil, it slowly seeps out of the source rock. The oil migrates until it is trapped in a reservoir rock layer (usually sandstone) that has an impenetrable seal layer (usually shale) above it.

Whether this constitutes "dinosaurs" depends on your definition. If you are discussing therapods, sauropods, and the various reptiles collectively referred to as "dinosaurs" in common culture then, with some statistically insignifigant exceptions, "no".