Environmental Engineering Reference
In-Depth Information
Choice of Radioactive Tracer Materials
In general, a radioactive tracer material should be chosen that is soluble or miscible
with the fluid to be profiled or traced. Since surveys may be run in oil, water, or gas
flows, several different substances are required. Table 6.1 lists oil, water-, and gas-
soluble tracers. Note that the half-life is listed for each material. The half-life for
most radioactive tracers is in the order of days or weeks. For safety reasons, radioac-
tive tracers are used only in injection wells. Their use in producing wells raises
problems with disposal of radioactive fluids at the surface and contamination of
separator and other surface equipment.
Table 6.1 Tracer materials
Predominant
Gamma
Isotope
Carrier
Half-life
Uses
Water-soluble tracers
Iodine-131
NaI in water
8.05 days
0.364 MeV
(80 %)
Waterflood profiles, channeling,
cement location
Iridium-192
Na 2 TrCl in
hydrochloric acid
74 days
0.46 MeV
(94 %)
Same as above
Oil-soluble tracers
Iodine-131
C 6 H 5 I in organic
solvent benzene,
gasoline
8.05 days
0.364 MeV
(80 %)
Oil-injectivity profiles,
oil-cement slurry location,
erratic results if water present
Iridium-192
Na 2 IrCl in
organic solvent
benzene, xylene
74 days
0.46 MeV
(94 %)
Same as above
Universal—Oil- or water-soluble tracers
Iodine-131
Special solvent
8.05 days
0.364 MeV
(80 %)
Profiles in oil or water or
oil-water mixtures
Iridium-192
Special solvent
74 days
0.46 MeV
(94 %)
Gas tracers
Iodine-131
Methyl iodide
(CH 3 I)
8.1 days
0.364 MeV
Gas-injectivity profiles. Methyl
iodine furnished in glass
ampules, boils at 72.2 °C or
162.2 °F
Iodine-131
Ethyl iodide
(C 2 H 5 I)
8.1 days
0.364 MeV
Gas-injectivity profiles. Ethyl
iodine furnished in glass
ampules, boils at 42.5 °C or
106 °F
Source : General Nuclear, Inc., Houston, Texas
Note : Aside from normal radioactivity hazard, methyl and ethyl iodides are very toxic gases with
low boiling points and must be handled accordingly. Neoprene O-rings also deteriorate rapidly in
the presence of these gases
 
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