Since the early 20th century, most of the world's helium supply has been extracted from natural gas as part of the nitrogen rejection process.
[1] To accumulate to an exploitable reservoir, helium must be trapped by a non-porous rock.
[2] In North America, most exploration activity centres on the Four Corners region, where the borders of the states of Arizona, Colorado, New Mexico and Utah intersect.
[3][4][5] Exploration in Tanzania shows reserves of 138 billion cubic feet.
[6] Grand Gulf Energy is drilling in the Leadville Dolomite Formation in Utah.