What time do organisms that get buried underground is a long series of several biochemical chemical reactions. Once organisms get buried, it’s a game of temperature, pressure, and bacteria that goes on for millions of years.
Let’s look at the typical timeline of an organism that gets buried.
First, the oxygen gets cut off once the buried organism is at a certain depth. This oxygen-free environment kicks off the anaerobic bacterial decomposition of the organic matter. Decomposition basically breaks down complex molecules of organic matter into simpler molecules. It becomes an insoluble matter called Kerogen if given a few thousand years.
These simpler molecules could be hydrogen and carbon, forming the hydrocarbon compound. The heat and pressure determine the type of hydrocarbon formed based on how the organic matter sinks through the layers. With the right temperature, pressure, and depth, a mix of solid, gaseous, and mostly liquid hydrocarbons would be formed over time (millions of years). This mixture is what you’d call petroleum (or crude oil). Technically this process is called Catagenesis.
So, the ‘time’ component acts as a very slow cooker that builds up pressure and heat. There’s a lot of factors involved, mind you. So ‘time’ plays the dominant role here, patiently facilitating all the right conditions like sinking, decomposition, heat, and pressure to form Kerogen, eventually Catagenesis, and trapping the oil in a reservoir. Time is the crucial ingredient here.
