A further (shorter) tutorial is in order I think!
At 09:59 03/09/2003 -0400, you wrote:
Greetings, Normally, I don't follow energy discussions... But, I have a query. Recently, a most respected and technically qualified friend visited, and among the other ideas he laid on me was the following: Oil (petroleum) is not created by the decay of biomass over eons. It is created by some form of bacteria.
I think maybe your friend is confusing two (fairly) separate sources of natural gas. As far as I'm aware, all the oil and gas fields which have been prospected (and they are known now in great detail all over the world, even in the Antarctic) lie at ancient river estuaries, even if some of these are now under the sea (as in the North Sea). The oil and gas is a product of the breakdown of the immense amounts of vegetation that were deposited in these estuaries from discarded vegetation from dense tropical rain forests of thousands of square miles in area. Each of these deposits would be like a gardener's compost heap -- but many square miles in extent and maybe miles deep! If sedementary rocks, such as sandstone, were subsequently laid down on top of these compost heaps then as the methane and propane (or the oil) were produced they would diffuse into the micro-crevaces in the overlying rock. And this is what is drilled into in your typical oil and gas fields. The gas or oil springs out or leaks out -- or is forced out by injecting high pressure water.
But natural gases, such as methane and propane, as a result of anaerobic decomposition, would also be produced by bacteria and small insect life in even moderately poor soils and this would happen across very large portions of the earth's surface, not just in the concentrated rain forests. If these layers were subsequently capped with water then, as the gases were produced they would diffuse into the water and if, further, very great pressure were exerted on these layers, or if they became very cold, as in permafrost regions, then the gases would be trapped within ice crystals. These deposits are called methane (or propane) hydrates. These are found in very extensive areas in deep water adjacent to continental shelves (that is, in areas where a previous land surface has subsided), and also, nearer the surface, in northern permafrost tundra regions. The amount of methane in these deposits is immense. Estimates of the amount of methane vary between quantities between 20 and 200 times the amount of natural gas in orthodox rock-type gas fields -- more than enough to keep the whole world going for at least hundreds of years.
However, there are two big drawbacks. For one thing, most of the deposits, though huge, have very low concentrations of methane and are not economic to extract. For another, the deposits would probably be very dangerous to exploit because the methane hydrates are liable to melt and collapse in an uncontrollable way. Under the sea in particular, the methane hydrate layers, perhaps hundreds of feet thick could suddenly start dissolving into a thick sort of water, causing immense slippages of nearby rock and coastlines. Already, oil drilling rigs have disappeared when ocean floors have suddenly given way when the drill head reached the tip of hydrate layers. Any deeper penetration could have caused major landslides -- of the sort that could drop hundreds of miles of coastline (and many miles inland) into the sea and produce earthwauke-type tsunami waves that could travel for thousands of miles across oceans. There is much evidence that these sort of immense landlsides have occurred in times past when sea levels dropped during ice ages and the pressure on the methane hydrate levels was reduced.
In short, methane hydrates are strictly off-limits! Too "hot" to handle. There may be places where it is known that the hydrates are both highly concentrated and are in restricted undersea valleys where they are hemmed in and therefore perhaps not too dangerous to tap into but, even so, the oil corporations, desperate though they are for more oil and gas resources, are not spending any money on research and development of these resources and are leaving it to governments, which carry out modest research programmes from time to time. Another possibility that has been considered is that if there were a collapse of a major methane hydrate field, then the atmosphere could become saturated with methane -- and this is a greenhouse gas that is 10 times more powerful than CO2 in its temperature-blanketing effect.
That seems to be the picture and this is why, despite the quite enormous quantities of methane down there, it never enters into scenarios for mankind's energy future, corporate or governmental.
KSH
The implications are that oil may be an unlimited resource, and that we are not drawing down on a resource that will become increasingly rare and expensive. Also: productive and long-term oil deposits are likely to be more common than commonly thought.
My reaction was skepticism, but this friend is no lightweight, has a very strong engineering and scientific background, and carries on an active and personal worldwide technology and science scan.
Your thoughts?
Cheers, Lawry
Keith Hudson, 6 Upper Camden Place, Bath, England, <www.evolutionary-economics.org>
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