Drilling water of the Siberian oil deposits and that from the ground waters of Yakutia are the objects of study. Tritium has been determined by liquid scintillation spectrometry with inductively coupled plasma and the element content – by mass spectrometry. Special equipment has been developed which allows managing little or no change in the physical properties of the fluids and separating the main salt matrix (inorganic salts, trace of oil and polymers) of the determined submicro elements and radionuclides (uranium, thorium and tritium isotopes). The development of the equipment has significantly improved the detection limit of uranium (20 ng/L), thorium (10 ng/L) and tritium (1 Bq/L), with the efficiency being 27 %.