So, Where Does Oil Come From?

Well, silly, it comes from oil wells, of course! Sorry, that was just too easy to pass up (and in some respects the best answer out there)! Really now, where does oil come from?

The truth is, no one is completely certain how oil originated, migrated and accumulated.

Organic

Prevailing wisdom, based on over a hundred years of production history, has it that crude oil was formed from layers of dead organisms lying on the sea floor for millions of years. Over time, sand, clay, and limestone layers covered the rich organic sediments, which are typically fine-grained shales, choking out oxygen and allowing bacteria to break down the organisms.

As the organic-rich sediment was covered with more and more layers of earth, the weight of the overburden caused pressure and heat to transform the organic material into one of the various phases of hydrocarbon (natural gas, crude oil, or bitumen) Scientists call this organic-rich sediment layer the source rock, as it is where oil is created.

It is estimated that it took millions of years to convert the organic matter into the quantities of hydrocarbon produced in the oil fields of today. As a result, oil is considered a finite resource. As the oil fields around the world are identified, and oil increasingly produced, the earth’s oil generating machine cannot keep pace, and the world’s overall oil balance declines.

Inorganic

Another novel theory for oil’s origin suggests that it is an inorganic product originating deep in the earth, between the mantle and the crust. Miles below theearth’s surface, it is theorized, the interaction of a now mobile, inorganic methane and high temperature pockets takes place and results in the condensing of crude oil.

An intriguing aspect of this theory is that oil is constantly being generated in numerous places around the world, and at rates that can continue to sustain our current way of life. So now, according to some, oil is not a limited resource after all.

It should be noted that this inorganic theory is held by a minority of industry professionals. The oil discoveries and development plans throughout the world have been based on the organic theory of hydrocarbon origination and a declining inventory. Seems to me like conventional wisdom wins the day.

Via  So, Where Does Oil Come From?

We also found this interesting piece by Christina Reed on Geotimes  from 2002 on J.F. Kenny’s problems regarding his ideas of inorganic origins of oil on earth. – Deskarati –

Inorganic origin of oil: Much ado about nothing?

Geoscientists are cringing as news reports dredge up what they have long considered a preposterous assertion about the origin of oil: that none of the fossil fuels found on this planet come from fossils. The idea, heavily debated in Russia during the 1950s and 1960s, holds that the world’s oil is not made of decomposed biological organisms; rather, it forms inorganically at near-mantle depths then migrates up to the crust.

The newest incarnation comes from J.F. Kenney, a self-proclaimed oil and gas driller from Houston who worked with three Russian scientists, including Vladimir Kutcherov of the Russian State University of Oil and Gas. Their paper on inorganic hydrocarbon formation, published in the Aug. 20 Proceedings of the National Academy of Sciences (PNAS), has generated coverage in NatureThe Economist and New Scientist and led to an interview of Kenney on National Public Radio (NPR). PNAS published the paper at the request of Academy member Howard Reiss, a chemical physicist at the University of California at Los Angeles. As per the PNAS guidelines for members communicating papers, Reiss obtained reviews of the paper from at least two referees from different institutions (not affiliated with the authors) and shepherded the report through revisions.

The paper examined thermodynamic arguments that say methane is the only organic hydrocarbon to exist within Earth’s crust. The report also discussed the hypothesis that high pressures of 25 to 50 kilobar or more are needed for establishing natural petroleum hydrocarbon molecules. The authors also included a description of laboratory experiments in Moscow that created petroleum products from marble, water and iron oxide under 50 kilobar of pressure and 1,500 degree-Celsius temperatures.

But the news stories, Kenney says, are written on the premise that “I have ‘developed a thermodynamic argument that demonstrates that the hydrocarbon molecules of natural petroleum cannot evolve spontaneously at the low pressures and temperatures of the near-surface crust of the Earth.’ Such is absolute nonsense.” To which many geologists would agree. But, Kenney adds, “The fact that the hydrocarbon molecules which comprise natural petroleum cannot evolve spontaneously at the low pressures and temperatures of the near-surface crust of the Earth has been known by competent physicists, chemists and chemical engineers for over a century. In my article, I only reviewed this knowledge briefly, using the efficient formalism of modern thermodynamics.”

Kenney’s slap in the face to the competence of modern geologists is not winning him any converts. Even astrophysicist Thomas Gold of Cornell University, who wrote two books on the subject of inorganic oil on Earth, is surprised by the media’s response. “There is nothing new about any mix of hydrogen and carbon at pressures of 40 kilobar or so, and temperatures of greater than 800 degrees Celsius, forming oil.”

Most commercial drilling occurs in sedimentary rock where source material temperatures range between 75 and 200 degrees Celsius. In the late 1980s and early 1990s, Gold spearheaded a project, which he says also involved Kenney, to illustrate the prospects of abiogenic oil and gas by drilling into crystalline rock in Sweden. But the granite did not yield an economically viable result.

Still, Kenney appears undaunted. During the interview on NPR, he said he found, while working with Kutcherov over the last 10 years, inorganic oil and gas fields in the northern flank of the Dnepro-Donetsk basin in the Ukraine that are greater than the entire reserves in Alaska.

Kenney and his Russian colleagues’ paper in PNAS is “an excellent and rigorous treatment of the theoretical and experimental aspects for abiotic hydrocarbon formation deep in the Earth,” says organic geochemist Scott Imbus of ChevronTexaco Corp. “Unfortunately, it has little or nothing to do with the origins of commercial fossil fuel deposits.”

While geologists agree that crude oil can come from inorganic means, the majority of commercially recovered petroleum, they say, is organic. And they are frustrated with advocates of this alternative theory who dismiss evidence of a biological origin or interpret organics in crude oil as contaminants. Such an idea is anathema to the well-established understanding that biomarkers in petroleum are a result of living organisms transforming the complex molecules, dying and then being subjected to burial processes that turn the biomarkers into petroleum products.

The idea of finding an abundance of crude oil ready for the tap at depths currently unreachable is tantalizing. But, says geochemist Alexei Milkov of the Deep Ocean Exploration Institute at the Woods Hole Oceanographic Institution and a graduate of Saint-Petersburg State University in Russia, “I’ve never met an industry geologist that uses abiogenic theory to find oil and gas fields, and that includes Russian industry geologists. These guys pay money for mistakes and can’t afford using wrong theories to continue exploration.” A key factor in deciding whether to put money in exploration of a frontier basin is the potential quality and extension of source rock, Milkov adds. “This strategy apparently works for them so far.”

That’s a pity, says Roger Sassen, deputy director of Resource Geosciences, a geochemical and environmental research group of Texas A&M University.

“The potential that inorganic hydrocarbons, especially methane and a few other gases, might exist at enormous depth in the crust is an idea that could use a little more discussion. However, not from people who take theories to the point of absurdity,” he says. “This is an idea that needs to be looked into at some point as we start running out of energy. But no one who is objective discusses the issue at this time.”

Christina Reed

Via Geotimes

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One Response to So, Where Does Oil Come From?

  1. alfy says:

    When the experts disagree the rest of us can only look on. There seems to be plenty of sound evidence for the biological origin of most terrestrial hydrocarbons. This does not preclude an inorganic origin for other hydrocarbons but the evidence appears to be much weaker. It is perfectly possible for both ideas to be correct, but just descriptive of two different situations.

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