Hopes that beneath the Earth’s crust lurk fathomless reservoirs
of hydrocarbons that will top up today’s fast-depleting oil and gas
fields are wrong, says a study.
The idea was launched a couple of decades ago by a US astronomer
and physicist, Thomas Gold.
He challenged the conventional idea that carbon-based fuels are
derived from long-decayed organic matter: tiny plants and animals
that, hundreds of millions of years ago, sank to the bottom of the
seas, when the Earth’s continental layout was very different, and
then became covered by sediment.
Gold believed that there was an ”abiogenic” — a non-biological
— source for the energy which came from the mantle, the layer
beneath the Earth’s crust.
He contended that the hydrocarbons were formed from a chemical
reaction between iron-bearing rock and searing heat and pressure at
depths ranging from 100 to 300 kilometers (60 and 180 miles).
These hydrocarbons then percolate up towards the surface,
gathering traces of other gases and microbes as they go, and then
hole up in porous rock, providing the commercial oil and gas fields
of today, he argued.
Gold stirred dreams that the Earth’s principal source of energy
could be almost unlimited thanks to this seepage of ”deep Earth
gas”.
But research by chemists at the University of Toronto in Canada,
published in Thursday’s issue of the British science journal
Nature, throws cold water on such hopes, although it confirms that
abiogenic gas does exist.
A team led by Barbara Sherwood Lollar took samples of methane
gas from a deep borehole at an Ontario mine, Kidd Creek, which
extracts lead, silver, zinc and cadmium.
The samples, taken at depths of 2,072-2,100 metres (6,800-6,900
feet), were then tested for isotopes of carbon and hydrogen — the
equivalent of a chemical ”fingerprint” — and these were indeed
found to abiogenic.
But the isotopic signature had no match with that of
hydrocarbons taken from commercial fields, which thus discounts
Gold’s theory of an ”outgassing” of hydrocarbons into the easily
accessible porous rock near the edge of the Earth’s crust.
There is no evidence to suggest that abiogenic gas makes ”any
significant contribution” to energy fields, the researchers say,
concluding: ”We can now rule out the presence of a globally
significant abiogenic source of hydrocarbons.” – AFP
