When was the first oil spring created?

How did oil come about?

The transformation

Marine organisms such as the unicellular foramniferee as well as animal and vegetable plankton die and sink to the bottom of seas and lakes.

In the depths of the seas and lakes, hardly any oxygen reaches the dead organic material. The result: The dead plankton cannot rot. Sediments such as sand and clay mix into the plankton layer over time. The so-called digested sludge is created: fine-grain, unconsolidated petroleum mother rock.

Further overlaying with sediments solidifies the bedrock and moves into the depths. Pressure and heat increase. At a depth of between 1,500 and 4,000 meters, at temperatures between 80 degrees Celsius and 150 degrees Celsius, ideal conditions prevail for the creation of crude oil: the bonds between the large molecules of the bedrock break open. Smaller molecules are created, the petroleum hydrocarbons. This turns a solid substance into a viscous oil.

The way up

The high pressure in the depths squeezes the oil out of the bedrock. It gets into the next, porous rock layer. Because it is lighter than water, it migrates up the pores, for example in sandstone - until it is caught in a "petroleum trap".

An impermeable layer, for example clay or salt, prevents further emergence of the coveted raw material. More and more oil droplets collect in the storage rock in a kind of dome - an oil reservoir is created.

So oil deposits are not huge, underground lakes, but rather porous rock layers that are so to speak like a sponge soaked with oil. The miraculous transformation of plankton into the black, stinky and sticky raw material can take between 10,000 and several million years. The way we get it out of the earth, nothing reminds of its origin, the microorganisms from seas and lakes.


Sometimes the oil makes it to the surface. Oil lakes are created when the fossil fuel rises unhindered, because no impermeable rock layer prevents this. The lighter components evaporate in the air. What remains is tough asphalt, which is why these hollows or lakes are also called asphalt lakes. Pitch Lake on the Caribbean island of Trinidad, an asphalt lake about the size of 40 football fields, has become famous.

Author: Harald Brenner