How and where are oil and gas formed?

OMV is producing around 300.000 barrels of oil and gas per day all around the world. But how did this precious raw material get 2.000 meters below the ground, what does it even consist of, and how did it get trapped?

The formation of oil and gas began ages and ages ago – more than 500 million years before the present. Since that time, the remains of organisms have been deposited in so-called sedimentary basins. Basins like this exist around the earth.
Jan Mayer, Junior Geologist, Exploration & Appraisal, OMV Upstream

From algae to oil and gas

What was once algae, plankton, fish, a tree, or maybe a dinosaur can be oil or gas today. Over millions of years, the remains of bacteria, plants, and animals bound together with fine sediment such as clay or shale and created layers on the seabed. These layers are called source rock. Over the years, they were covered with younger sediments and together with the sedimentary basin they sank deeper and deeper into the earth’s crust. The remains of organisms were converted partly into oil and gas through bacterial activity or the lack of oxygen, and heat in the deep subsurface.

Find more information here: Formation of oil and gas.

A few facts:

•  The word petroleum comes from Latin and means rock oil.
• One of the sedimentary basins richest in oil and gas lies in the Arab world and is suspected to contain around 50 percent of the world-wide reserves in oil.
• Even the Babylonians coated their roads with oil.

Getting trapped

„In order to be able to extract the raw materials, they literally first have to get trapped,“ explains Jan. „The newly formed hydrocarbons don’t just remain below the earth’s surface in the source rock; they migrate their way back to the surface over millions of years. They continue rising until they reach a porous layer, such as sandstone or carbonate rock.“

Oil and gas then accumulate in the tiny hollow spaces between the grains of sand and other pores in these reservoir rocks. And if the rock layer above this is impermeable, such as shale, they can’t get any further. The raw materials are trapped.

Southern Tunisia is home to a very old sedimentary basin, where oil and gas fields of OMV are located. The rock here is about 440 million years old. The Vienna Basin in Austria has been sinking into the earth’s crust for about 18 million years and is quite young in comparison; Dinosaurs had long been extinct by then.