Helium gas drives us to new perspectives and geological insights
Helium (from Greek translit. Helios, lit. ‘Sun’) is a chemical element with atomic number 2.
Helium was recognised as an element in 1895, but the bright yellow Helium lines in the solar spectrum were first noted, but not identified, in 1868.
Helium accounts for about 23% of the mass of the universe, so it is the second most abundant element after hydrogen.
There are two naturally-occurring isotopes, Helium-3 and Helium-4, which may be either primordial or radiogenic in origin.
Most terrestrial Helium is created by the natural radioactive decay of heavy radioactive elements (thorium, uranium), as the alpha particles emitted by such decays consist of Helium-4 nuclei and a few other elements that may either be components of some mineral deposits or be situated in the basement or country rocks.
Terrestrial Helium is a non-renewable resource because Helium is a very light element, does not accumulate in large quantities in the atmosphere since Earth’s gravity is not sufficient to prevent its gradual escape into space. Hydrogen is lighter, but it's common on Earth because hydrogen is captured in molecules of water or organic compounds. Helium, on the other hand, forms no compounds in nature even with itself.
In recent decades Helium has become a key resource in our high-tech world. The noble gas is used in cryogenics, MRI scanners, welding, deep-sea diving, fiber-optic cables and computer chips used in cell phones and computers.
Helium concentration on Earth 5.2 ppm by volume in the atmosphere and small amounts occur in radioactive minerals, meteoric iron, and mineral springs, great volumes of Helium are found as a component in natural gases (up to 11%) and oil (7ml/l).
Helium is produced as a minor constituent of natural gas and coexists with natural gas due to the same migration and trapping processes that create "gas" accumulations in the subsurface. In natural gas reservoirs, Helium concentrations above 0.3% are considered economically viable.
Helium gas (98.2% pure) is isolated from natural gas by liquefying the other components at low temperatures and under high pressures. This a low-temperature separation process called fractional distillation.
Commercial Helium systems have been found to date as a serendipitous by-product of petroleum exploration.
Inert noble gas
Elements in the universe
Helium presence on the earth
Helium accumulations and migration
Being a highly diffusive and inert gas, Helium constantly migrates vertically from crystalline basement through micropores and microfractures of sedimentary cover forming Helium microseepage at the earth surface.
While migrating to the earth surface Helium can be temporary captured and accumulated in Helium traps – specific geological structures of enhanced Helium capacity.
Oil and gas, geothermal and natural occurring hydrogen deposits are efficient Helium traps due to significantly higher Helium solubility in these elements compared to formation water and surrounding dry fractures.
After reaching saturation limit traps are subsequently degassed, releasing high Helium concentrations which migrate to the surface using the same advection mechanism.
Due to its unique properties like lightness, small molecular size and inertness, Helium migrates mainly vertically to the surface, where it forms anomalies. High concentrations of Helium at a certain location on the earth's surface indicate the presence of hydrocarbons, geothermal reservoirs, natural hydrogen and helium reservoirs in the underlying section.
Helium has a HIGH migration ability
Helium has a MAXIMUM vertical migration path through sedimentary cover to the surface
Helium Subsoil Gas as a resource indicator in Exploration
The Soviet School of Geochemistry has been considering Helium as a possible pathfinder for oil and gas, geothermal and studying the subsurface Helium for decades, all over the Soviet Union.
During this time, numerous research teams worked in Germany, the USA, Italy and Australia. Numerous publications have been written and concluded regarding the prospects for using Helium as an indicator of certain deposits.
According to the international scientists, Helium subsoil gas can be used as a direct or indirect resource indicator in exploration:
deposits containing uranium and/or thorium in sufficient quantities to act as an adequate helium source (uranium deposits, some coals, mineral sands, carbonates);
liquid and gaseous hydrocarbons, which are enriched in helium derived from the basement or thorium- or uranium-bearing source rocks;
deposits associated with (and emplaced along) faults that act as pathways for the escape of basement-derived helium;
geothermal areas, which are the focus for the release of helium contained in juvenile or
circulating meteoric water;
natural helium deposits;
natural hydrogen deposits, in some geological conditions where helium and natural hydrogen can be found together or associated with methane.
Additionally, Helium leaks along unmineralised faults, including active ones, and in consequence its detection supports locating faults in areas of poor outcrop.
According to the research work carried out, Helium subsurface surveying became a common procedure in Soviet resource exploration for detecting faults and placing oil and gas wells, including in the absence of good geophysical information.
Both Western and Soviet scientific schools agree that heliometric data can be used as an indicator of faults and certain deposits, but existing limitations (standard geochemical sampling methods, sensitivity of instruments, etc.) bring a lot of uncertainties in the heliometric data quality and reliability.
These limitations have been a major problem in the use of heliometric data as a robust natural resource indicator for the past decades before Actual Geology introduced its' unique all-inclusive methodology and took it to the commercial life.
Helium anomalies on the surface provide SIGNIFICANT information about geology and resource presence