Earth's limitless oil and gas reservoirs are a myth
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 km (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 the issue of the
British science journal Nature, throws cold water on such hopes, although it confirms that abiogenic gas does
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 ft), 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."