September 20, 2004
AND MORE:
Petroleum under pressure (PhysicsWeb, 14 September 2004)
Scientists in the US have witnessed the production of methane under the conditions that exist in the Earth's upper mantle for the first time. The experiments demonstrate that hydrocarbons could be formed inside the Earth via simple inorganic reactions -- and not just from the decomposition of living organisms as conventionally assumed -- and might therefore be more plentiful than previously thought.Methane is the most abundant hydrocarbon found in the Earth's crust and is also the main component of natural gas. Reserves of natural gas are often accompanied by petrol, usually only a few kilometres below the Earth's surface. The possibility that hydrocarbons might exist deeper in the Earth's mantle, or could be formed from non-biological matter, has been the subject of debate among geologists in recent years.
To explore these questions further Henry Scott of Indiana University in South Bend and colleagues at the Carnegie Institution in Washington, Harvard University and the Lawrence Livermore National Lab subjected materials commonly found in the Earth's crust to temperatures of up to 1500°C and pressures as high as 11 gigapascals (Proc. Natl. Acad. Sci. to be published). These conditions are similar to those found in the Earth's upper mantle.
Scott and co-workers squeezed together iron oxide, calcium carbonate and water between two diamonds with flattened tips while heating up the device. The advantage of the "diamond anvil cell" technique is that the sample can be analysed in situ -- through the diamonds -- using a variety of spectroscopic techniques. The US scientists found that methane was most readily produced at relatively low temperatures of 500°C and pressures of 7 gigapascals or below.
That Humbug Peak just keeps receding. Posted by Orrin Judd at September 20, 2004 9:58 AM
Does anything in the article confirm new "production" of any reserves, much less replacement in scale of depleted reserves? Maybe this is good news for people in AD 3000 or AD 30,000 or AD 30,000,000, but it probably won't affect us.
Posted by: Chris Durnell at September 20, 2004 11:39 AMChris: The theory that petroleum is produced geologically is at least ten years old. It was sparked by the observation that old oil reservoirs were refilling faster than could be accounted for by the orthodox theory of biological rendering.
Once scientists started to examine the orthodox theory, they discovered that there was no proved mechanism for starting with dinosaurs (actually, plant biomass predating the dinosaurs) and ending up with petroleum. The main evidence for the theory of biological origin was that organic molecules are found in petroleum products. However, life is so abundant that it is difficult to take anything out of the earth, let alone billions of gallons of oil, without coming across organic molecules.
The geological origin theory still has not been proved, but it does seem to fit with the facts (i.e., we're swimming in oil) better than the biological theory and now a possible process has been demonstrated in the laboratory. As far as I know (and I am far from an expert), no method for the biolgical origin theory has ever been demonstrated.
Posted by: David Cohen at September 20, 2004 4:47 PMDavid:
Swimming in methane, not oil.
It's still usable as an automotive fuel, but it's not what we're currently using, and inferior to petroleum.
In fact, according to Henry Scott, et al., methane is readily produced under pressure, at 500° Celsius.
According to the Chevron corporation, crude oil is usually destroyed at 500° Fahrenheit, a much lower temperature than is required to produce methane in the Earth's crust.
The "sweet spot" for crude oil is between 200° - 350° Fahrenheit.
However, Chevron also estimates, (I suspect very roughly), that there are a trillion barrels of oil yet to be produced in proven fields, and another ten trillion barrels of oil available globally in bitumen, shale oil, by tapping oil fields in very difficult areas to work in, and by using fairly expensive recovery methods to strip every drop out of fields that have stopped producing using cheaper methods.
In other words, it's not so much that we're running out of oil, as it is that we're running out of cheap oil.
Posted by: Michael Herdegen at September 21, 2004 12:59 AMDavid:
Swimming in methane, not oil.
It's still usable as an automotive fuel, but it's not what we're currently using, and inferior to petroleum.
In fact, according to Henry Scott, et al., methane is readily produced under pressure, at 500° Celsius.
According to the Chevron corporation, crude oil is usually destroyed at 500° Fahrenheit, a much lower temperature than is required to produce methane in the Earth's crust.
The "sweet spot" for crude oil is between 200° - 350° Fahrenheit.
However, Chevron also estimates, (I suspect very roughly), that there are a trillion barrels of oil yet to be produced in proven fields, and another ten trillion barrels of oil available globally in bitumen, shale oil, by tapping oil fields in very difficult areas to work in, and by using fairly expensive recovery methods to strip every drop out of fields that have stopped producing using cheaper methods.
In other words, it's not so much that we're running out of oil, as it is that we're running out of cheap oil.
Posted by: Michael Herdegen at September 21, 2004 1:00 AMI believe the biologic origin of petroleum is posited to be the oils stored in many unicellular animals and plants.
The reason the biogenic origin is preferred, so far, is that the range of biological fossils found near oil is not random but preferentially of marine origin.
There seems to be a fairly strong connection between marine deposits and petroleum.
Of course, that could be because there weren't any land organisms when the petroleum was made, but if it were abiogenic, you'd think it would be picking up later land microfossils sometimes.
(Before I met her, my wife used to count microfossils for a petroleum geologist.)
Posted by: Harry Eagar at September 21, 2004 2:21 AMHarry: Part of the abiogenic theory (thanks, a much better word) is that the petroleum is not made where it is found. Rather, the theory is that it is made much deeper and seeped up into the reservoirs, filling them over the centuries. Why the reservoirs tend correlate with marine fossils I have no idea. (Porosity, maybe?)
Michael: The theory is that all hydrocarbons, including petroleum, are abiogenic. This experiment showed that methane can be made, in the lab, abiogenicly.
Posted by: David Cohen at September 21, 2004 4:58 PMIt's a moot point if the generation rate of new oil (biogenic or abiogenic) is only a few percent of the consumption rate.
You'll still be heading for what Wall Street calls a "correction" (like that three-car correction on I-5), just that it'll be a little shallower slope, eased by the new oil generation rate.