The geologic formations that contain oil and gas deposits also contain naturally-occurring radionuclides, which are referred to as "NORM" (Naturally-Occurring Radioactive Materials):
Uranium (and its decay products)
Thorium (and its decay products)
Radium (and its decay products)
Lead-210.
Geologists have recognized their presence since the early 1930s and use it as a method for finding deposits.
Much of the petroleum in the earth's crust was created at the site of ancient seas by the decay of sea life. As a result, petroleum deposits often occur in aquifers containing brine (salt water). Radionuclides, along with other minerals that are dissolved in brine, precipitate (separate and settle) out forming various wastes at the surface:
Mineral scales inside pipes
Sludge's
Contaminated equipment or components
Produced waters.
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