Because of its weak atomic weight, helium it is not retained in the Earth atmosphere (it escapes out to space).
For that reason there is no “original” helium. All existing helium in our planet was formed from radioactive transformation of other elements, including the fission of uranium and thorium.
The concentration of helium in the atmosphere is extremely low (0.0005%).
Moreover helium is not found in any organic matter either alive or dead.
However, hydrocarbon deposits have high helium contents which may reach 7% or more.
In the United States large amounts of helium were found in the gas fields of the Great Plains, and since then the country has led the heleum production worldwide.
Oil fields also contain relatively high concentrations of helium, generally below 0.05%. There are many oil fields with higher proportions of 0.1% helium and even of the order of 0.5% (for example, Eastern Siberia fields present helium proportions of between 0.2 and 0.6%).
The concentration of helium in natural gas and oil are respectively 1,000 and 10,000 times higher than those found in the atmosphere.
In hydrocarbon deposits, where helium contents are high the proportions within the gases mixture (including hydrocarbons and nitrogen plus helium) are curiously similar on very large areas regardless of the geological heterogeneities.
The obvious conclusion is that helium is not of local origin or coming from each of the geological provinces (in which case their tenors should vary) but it has a unique deep source that feeds evenly all considered regions (ie with the same proportion of the various gas mixtures).
As helium is a chemically inert element is not possible to imagine any chemical process that allows helium concentration in its migration.
According to Thomas Gold (2001), helium enrichment of hydrocarbons provides a good measure of the depth to which the hydrocarbonaceous fluids started moving upwards.
This author points out that the partnership between helium and hydrocarbonaceous fluids is so widespread that appears to prove that helium was collected and transported by the rising hydrocarbons.
Helium atoms are generated in extremely diffuse radioactivity processes in the rocks. It would be very difficult to explain the migration of helium atoms without a carrier fluid. If helium could migrate on their own would finally accumulate in “helium fields.” It does not happen. However there are many accumulations of hydrocarbons with high content of helium, showing that it was the carbonaceus fluids who carried it creating the observed geochemical anomalies.
From "Unexhaustible? Oil and natural gas", Danilo Anton, Piriguazú Ediciones
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