Geology & Geophysics News

Tanzanian Volcanoes May Hoard Helium Ready for the Taking

Sweet spots of volcanic heat that are not too close to active eruptions may hold the world's richest reservoirs of the scientifically and medically important gas helium.

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Volcanologist Peter Barry spent years in the Great Rift Valley of Tanzania as a graduate student studying the noble gases released at hot springs, asking broad scientific questions about the region’s nearby volcanoes. But unbeknownst to Barry, beneath his feet lay a precious supply of helium gas potentially more concentrated than any reservoir of the element previously discovered.

“The helium was under our noses the whole time, but we weren’t thinking about developing resources and were instead asking broader scientific questions about the volcanoes themselves,” said Barry, now a postdoctoral researcher in the Department of Earth Sciences at University of Oxford in the United Kingdom.

A team led by Barry recently found evidence for unusually rich helium deposits across the Rift Valley. One apparent reservoir of the gas offers the unheard-of helium concentration of more than 10% by volume. At sites around the valley, the researchers more commonly found helium in the 1.5%–2.5% range.

The world’s 33 helium plants extract the element from natural gas, and helium rarely composes more than 0.7% of the total volume. At large natural gas plants in Qatar, helium concentrations sometimes barely reach 0.05%. In contrast, the more highly concentrated helium in Tanzania appears to be mixed mainly with nitrogen, from which helium is more easily separated.

Helium finds wide use as an ultracold liquid in MRI equipment and other medical devices, spacecraft, and scientific facilities such as particle accelerators. The gas changes to a liquid at the extraordinarily low temperature of −269°C and therefore can be used to cool superconducting magnets and other devices. An MRI scanner contains about 1500–2000 liters of liquid helium to cool its magnets.

The new findings of high-concentration helium may profoundly alter the way the element is extracted from the Earth, according to Barry and other helium experts.

“In Tanzania we can drill a well to target just helium. This is … unique—no one else is doing this,” said Barry. His team presented evidence of the high-concentration helium reservoirs on 27 June at the Goldschmidt Conference in Yokohama, Japan. The findings also may clarify how volcanic activity influences the richness and locations of natural helium reservoirs.

The Goldilocks Zone

Helium-One geologist takes gas samples at hot spring.
A geologist with Helium One takes gas samples at a hot spring using a funnel that feeds into an impermeable copper tube. Credit: Peter Barry

Barry returned to Tanzania to survey helium reserves at the request of Helium One Ltd., a start-up mining company that was registered in the British Virgin Islands in 2015. The company had found a 1967 scientific paper indicating rich helium deposits in the Rift Valley’s thermal springs and wanted Barry and his colleagues to verify the findings.

To test helium concentrations, the researchers took samples of gas bubbling from the hot springs reservoirs by means of a funnel connected to a copper tube. Surface gas samples typically reflect true subsurface concentrations, Barry told Eos.

Samples taken within 20–30 kilometers of a trio of active volcanoes contained helium at a concentration of only 0.0005%, according to Barry. However, helium concentrations in samples taken in the Rungwe area of the Rift Valley, about 150 kilometers from those volcanoes, reached as high as 2.5% helium. Less than 50 kilometers from the Hanang and Labait volcanoes, in another Rift Valley region called Balangida, the team measured the extraordinary concentrations of 10.2% helium.

On the basis of the findings, Barry and his colleagues suggest that most deposits of concentrated helium gas occupy a Goldilocks zone that lies at a “just right” distance from volcanoes. Volcanic heat can liberate helium from ancient rock. However, the researchers speculate, volcanic gases like carbon dioxide (CO2), abundant near erupting volcanoes, may then dilute the helium, driving concentrations down. The location of the Goldilocks zone would depend on factors such as how active the volcanoes are and which volcanic gases are present, Barry said.

“If volcanic gases are causing dilution, then you will see high CO2 and low helium closest to the active volcano. Farther away, the helium will dominate. This is what we are seeing,” said Diveena Danabalan, a Ph.D. student from Durham University, also in the United Kingdom, who worked with Barry on the sampling. Because Hanang and Labait are relatively inactive volcanoes for the region, they might not greatly dilute helium by producing large amounts of CO2, Danabalan added.

Helium Glut

The Tanzania find comes on the heels of a period of severe instability in the global helium market, which was valued in 2015 at $700 million. Contrary to the popular perception that helium stocks are running out, the world supply currently significantly outstrips demand. That abundance follows a shortage from 2011 to 2013 when several new helium production sites delayed opening, maintenance work at natural gas plants idled some existing suppliers, and remaining sites held production steady because they lacked costly cold-temperature storage to hold additional output.

In response to the shortage, producers of MRI scanners began recovering and recycling helium. Recession in Europe and Asia also reduced demand just as the delayed sites began to increase supply. Adding to the oversupply, new producers have recently come online in the United States and Algeria. Today, most helium production sites are only running at 50% capacity, said Ralf Gubler, a senior principal analyst covering industrial gases at IHS Chemical in Zurich, Switzerland.

If the Tanzanian measurements lead to accessible reservoirs of helium not mixed with natural gas, those new sources may prevent future price shocks like the ones that debilitated past markets, according to Gubler. When a liquefied natural gas plant that’s also a helium source requires maintenance or if production stalls, the helium market loses some of its supply, he noted. Tapping reservoirs of helium gas rather than natural gas containing helium might also prove more profitable. “If the helium concentration at the new source in Tanzania is really high, the producers will benefit from lower costs,” said Gubler.

The discoveries in Tanzania aren’t expected to make a big difference to the world reserves. The estimated 1.53 billion cubic meters of helium gas there would meet only about 9 years of global helium demand, according to Robert Jolley, field manager at the U.S. Federal Helium Reserve in Amarillo, Texas. Rather, “it is the high helium concentrations [that] are significant, as opposed to the total amount of gas, which is not huge compared to other helium-producing regions,” said David Hilton, an isotope geochemist at Scripps Institution of Oceanography in La Jolla, Calif.

For now, Josh Bluett, technical director at Helium One Ltd., hesitates to claim too much, noting that “it will require further geophysical surveys and drilling to prove up the potential and to ultimately realize productive helium reserves.”

—Amy Coombs, Editorial Intern

Citation: Coombs, A. (2016), Tanzanian volcanoes may hoard helium ready for the taking, Eos, 97, doi:10.1029/2016EO056641. Published on 28 July 2016.
© 2016. The authors. CC BY-NC-ND 3.0
  • Alton Brown

    The high helium concentrations in gases reported here are not a new discovery nor is this the first time a helium potential has been proposed for Tanzania. The 1967 paper referred to in this article (James, T. C. 1967, Thermal springs in Tanzania: Applied Earth Science, vol. 76, p. B1 -B18) provides a bit of the history behind the Tanzanian helium exploration. Many of James’ data were collected as part of an earlier economic helium evaluation by the UK Atomic Energy Authority in the nineteen fifties. In addition to widespread spring and gas sampling, shallow wells were drilled at two sites to evaluate economic potential. This search was ultimately unsuccessful.

    James interpreted the helium-rich gases to be exsolved from spring water. The helium and nitrogen
    concentrations in the gas, the spring water flow rates, and gas flow rates presented by James can be used with Henry’s constants from Wilhelm et al. 1977 (Chemical review, v. 77, p. 219-262) to calculate the depth below surface at which gases exsolved from the water. Most gases evolved at shallow depth (<20 m), with the deepest gas evolved near 160 m. Depth of exsolution calculated from nitrogen and helium are similar in
    the same spring, indicating similar sourcing of both nitrogen and helium from the aquifer water near the spring. There is no correlation between helium concentration and the depth of exsolution.

    Because the gases exsolved from water at shallow depth, their compositions cannot indicate the presence or the composition of any deep subsurface gas accumulation. The shallow exsolution depth demonstrates the aquifer water is seriously undersaturated with gas at pressures and depths expected for economic helium accumulations (1 – 3 km). Water with such low gas saturations never equilibrated with a high-pressure gas phase, be it a helium accumulation or a migrating gas.

    Absence of interaction with a high pressure gas phase is substantiated by both James’ data and more recent studies. The shallow drilling for helium in the fifties encountered only aquifer water with dissolved helium partial pressure similar to that of the nearby natural springs. The He/20 neon ratios reported by Danabalan et al. (2016 Goldschmidt Conference abstracts) indicate that Tanzanian gases had two orders of magnitude greater interaction with water than did the gases in North American wells. This higher water interaction is consistent
    with an absence of a gas phase interaction until exsolution near the springs.

    Of course theses data do not mean that there could not be high helium gases in rift-fill sediments in Tanzania. Helium potential can be assessed by presence of traps, adequate seals, and potential mechanisms for formation of a deep subsurface helium-rich gas phase. However, compositions of gases exsolved at shallow depth from springs tapping shallow fractured basement aquifers cannot be used as proof for the presence of a subsurface gas accumulation or the helium concentration within a deep subsurface gas phase.