[mountn man]

When an oil field is 5 miles below the surface of the earth, 1000's of feet in depth and miles across, thats an AWFUL LOT of trees and animals to be packed into an area. Why is the oil pocket 5 miles down? Was the earth at one time a lot smaller, that what is 5 miles down, was once the surface of the earth. When plants and animals die, they decompose into dust and dirt. What prevented normal decomposition, that allowed heat and pressure to do its thingy versus decomposition?

If you'd take the Amazon forest and INSTANTLY covered it, crushed it, and heated it, the trees and plants and animals would crush down to about a foot thick, not 1000's of feet.

I've read that oil wells, once thought dried up, are once again filling up with oil. Suggesting that oil creation might be a recurring process.

[Sherman Logan]

There is a spectrum of fuels from peat to various types of brown coal, to bituminous coals to anthracite.

It appears pretty clearly that the harder and more energy-containing types are formed from peat by the action of heat and pressure underground.

As far as animals and plants being unable to form thick deposits, there are numerous layers of limestone around the world hundreds of feet thick. It is pretty clear that limestone is primarily formed from the shells of marine organisms.

[PBinTX]

Oil doesn’t exist as a lake below ground, so your example about crushing down the rainforest is flawed. Oil occurs in the pore spaces of rocks like sandstone and there may only be 20 to 30% porosity for the oil to occupy, like water in a sponge. You can get a thousand feet of oil because the oil is trapped by a structural or lithologic trap, pooling oil in a limited space that drained from a much larger area. A thousand feet of oil saturated rock is not unusual.

[Ann Archy]

I have always thought oil was produced by PRESSURE and it either squeezed out the oil in the rocks or else melted the rocks into oil.

How anyone believes it's plants and animals......MOSTLY IN A FEW PLACES on earth....is beyond me. I have had geologists wanting to COMMIT me for this!!

[wolf78]

When an oil field is 5 miles below the surface of the earth, 1000's of feet in depth and miles across, thats an AWFUL LOT of trees and animals to be packed into an area.

Except coal is from forests, oil is from oceans, i.e. plankton.

When plants and animals die, they decompose into dust and dirt. What prevented normal decomposition, that allowed heat and pressure to do its thingy versus decomposition?

Hogwash. Dust and dirt, i.e. the mineral content is just a few percent. Most is carbon, oxygen and hydrogen. Hydrogen and oxygen evaporate partly as water, carbon together with hydrogen and oxygen is consumed by other animals and plants (ever heard of carbs?), turned into CO2, which together with the water nourishes new plant life. If you now take the biomass, remove it from the circle of life, heat and pressurize it, you get hydrocarbons like crude oil and natural gas (fossil) or synthetic biomass-to-liquid fuels (industrial).

What isolates the biomass from the natural recycling process is twofold: In the case of forests and moors it's a continuous process, some biomass is always lost to the ground. In the case of ocean plankton it's the deep sea environment with high pressure and low oxygen.

If you'd take the Amazon forest and INSTANTLY covered it, crushed it, and heated it, the trees and plants and animals would crush down to about a foot thick, not 1000's of feet.

If you repeat the cycle for hundreds of thousands / millions of years, you only need a few milimeters (not even a foot) per year to get to the amount of oil there is today.

If the origin in biological, one would expect to find remains of clearly biological origin, but perhaps heat and pressure could eradicate the evidence. If the origin is not biological, some biological “contamination” might still have occurred. Perhaps the “science” on this would still focus on the prevalence or relative absence of biological material, and the use of judgment.

That science has been done decades ago. The composition of petroleum, especially of trace elements contained in the petroleum like sulfur etc. strongly suggests a biological origin. Also the location of oil fields relative to the historic location of oceans suggests a biological origin. That doesn't mean that abiotic hydrocarbons don't exist. It just means that large-scale abiotic generation of petroleum is very, very unlikely.

Sherman Logan is a 100% correct.