The helium that we use today is found exclusively in natural gas deposits.  In 1906, a well that was drilled three years prior in Dexter, Kansas was analyzed and found to contain a very high 1.84% helium concentration.  This well, and analysis on subsequent wells, ushered in the American helium industry under the guidance of Dr. Richard Moore.  Prior to this discovery, the only helium that was able to be sequestered was from treating uranium-based rocks or gathering coal mine gas, both of which can only generate minute volumes of the gas.

Helium is formed through the radioactive decay of the heavy isotopes, Uranium-238, Uranium-235, and Thorium-232.  Uranium-238 is the most common isotope found in Uranium deposits making up roughly 2 ppm (parts per million) of crustal abundance. The isotope Uranium-235 is rare (0.015 ppm) and is the isotope used to induce fission for weapons and reactors.  Thorium-232 (10 ppm) and Uranium-238 are the primary isotopes responsible for helium generation.  As these isotopes continue in their decay chain (ultimately to stable lead isotopes), the three primary radioactive particles released are: alpha (a helium nucleus), beta (an electron), and gamma (X-rays).  The alpha particle consists of two protons and two neutrons and when it attracts two electrons, a helium atom is born.  Nearly all helium formed within the earth’s crust is through this decay chain cycle.  This decay chain cycle is also responsible for much of the earth’s internal heat.

Throughout the mid-continent, known high-helium concentrations exist where there is ample Uranium and Thorium in the basement “granitic” rock.  With the help of tectonic activity (i.e. faulting) and the brittle nature of the granites, helium will be expelled up into the sedimentary column.  In all cases, helium requires a carrier gas (nitrogen) so it will flow and ultimately collect in a gas reservoir.  Helium is always found with nitrogen and as helium concentrations rise, so too does the nitrogen concentration.  The opposite, however, is not always the case:  high nitrogen does not necessarily imply high helium.  Carbon Dioxide is also found in some helium-bearing formations but the presence of this gas is primarily due to its proximity to ancient volcanic activity.

The most important factor in a helium-bearing field is the presence of a cap rock or seal that is impermeable enough to withstand helium leakage.  This is the primary reason why we do not see more helium fields throughout the world. 

The helium found today comes from fields where 1) the basement rock is rich in Uranium and/or Thorium, 2) there is heavy deep-seated faulting so the helium can escape, and 3) there is a seal strong enough to keep it underground.

For further information on helium exploration, please read the short article Helium Exploration, by Bo Sears.

For further information on the earth’s production of helium, please click the following link written by Dr. Mike Reimer:  Helium Detection as a Guide for Uranium Exploration