Enhanced radioactivity due to natural oil and gas production and related radiological problems

Increased gamma radiation detected incidentally a few years ago in a North German oil field was traceable to radioactive scale. At the request of the Federal Ministry of the Interior a survey program was then established for dose rate measurements at various production sites, assessment of the radionuclide content of brines and scale and the Rn-222 content of natural gas. Dose equivalent rates of up to 50 mu Sv/h have been measured at the external surface of storage tanks for brines, but 73% of the 160 sites investigated did not show an increase above the natural background. Brines from gas fields contained Ra-226 of up to 286 Bq/l and scale of up to 1 kBq/g. In brines and scale from oil fields Ra-228 was usually the predominant radionuclide. Some samples contained "unsupported" Pb-210 and even Ac-227, too, but practically no uranium or thorium. The Rn-222 concentrations in natural gas samples varied between 0.004 and 4 Bq/l with a mean value of 0.6 Bq/l. It is shown that the radiation exposure due to natural gas consumption is negligible but some other problems or radiological relevance are recognized.