State of Current Research
The weight of evidence currently shows that petroleum is derived from ancient biomass. However, it still has to be established conclusively, which means that alternative theories like abiogenic petroleum can't be dismissed for now. The initial evidence was based on the isolation of molecules from petroleum that closely resemble known biomolecules (Figure).
Petroleum geologists agree that oil originates from to vast quantities of dead marine plankton or plant material that sank into the mud of shallow seas. Under the resulting anaerobic conditions, organic compounds remained in a reduced state where anaerobic bacteria converted the lipids (fats, oils and waxes) into a waxy substance called kerogen.
As the source rock was buried deeper, overburden pressure raised temperatures into the oil window, between 80 and 180 °C. Most of the organic compounds degraded into the straight-chain hydrocarbons that comprise most of petroleum. This process is called the generation kitchen. Once crude oil formed, it became very fluid and migrated upward through the rock strata. This process is called oil expulsion. Eventually it was either trapped in an oil reservoir or oil escaped to the surface and was biodegraded by soil bacteria.
Oil buried deeper entered the "gas window" of more than 160 °C and was converted into natural gas by thermal cracking. This gives the prediction that only unassociated gas and not oil will be found below a certain depth. At greater depths, even natural gas would be pyrolyzed.
A 2006 review article by Glasby presented arguments against the abiogenic origin of petroleum on a number of counts.
Read more about this topic: Abiogenic Petroleum Origin
Famous quotes containing the words state of, state, current and/or research:
“Clay answered the petition by declaring that while he looked on the institution of slavery as an evil, it was ‘nothing in comparison with the far greater evil which would inevitably flow from a sudden and indiscriminate emancipation.’”
—State of Indiana, U.S. public relief program (1935-1943)
“I can never suppose this country so far lost to all ideas of self-importance as to be willing to grant America independence; if that could ever be adopted I shall despair of this country being ever preserved from a state of inferiority and consequently falling into a very low class among the European States.”
—George III (1738–1820)
“Without the Empire we should be tossed like a cork in the cross current of world politics. It is at once our sword and our shield.”
—William Morris Hughes (1864–1952)
“The great question that has never been answered and which I have not get been able to answer, despite my thirty years of research into the feminine soul, is “What does a women want?””
—Sigmund Freud (1856–1939)