MANAGEMENT OF NORM IN THE PETROLEUM INDUSTRY Akpojevwa Tega Naomi, october 2016 | Page 17

Figure 1.2 Radioactive Decay in Thorium and Uranium Series.
Decay of these unstable radioactive elements produces other radionuclides that,
under certain conditions (depend upon pressure, temperature, acidity etc) in the
subsurface environment are mobile and can be transported from the reservoir to
the surface with the oil and gas products being recovered.
1.2.3 NORM in oil and gas Production:
1.2.3.1
Thorium and Uranium:
As an oil reservoir is a reducing environment, both Thorium (Th) and Uranium
(U) prefer the solid rock phase and do not dissolve in the aqueous or oily phase.
Consequently the top of both series remains with reservoir rock and can only
appear in natural concentrations at the surface during drilling operations.
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