Hydrogen & Oxygen isotopes of water
These isotopic analyses are performed at the IFE laboratory in Kjeller.
Oxygen isotope analyses
H2O(l) is equilibrated with CO2(g) at 30°C for 24 hours, whereupon the δ18O composition of CO2 will reflect that of the original water sample. Impurities are separated from CO2 on a Poraplot GC column before on-line determination of δ 18O, using a Thermo DeltaXP isotope ratio mass spectrometer.
Hydrogen isotope analyses
H2O(g) is reduced with Zn(s) to H2(g) and ZnO(s) in sealed, evacuated quartz vessels at 900°C. The δD composition is determined by a Horizon isotope ratio mass spectrometer from NU-Instruments.
Inferences of reservoir rock diagenesis can be adversely affected by:
- Lack of knowledge of parent meteoric water isotopic composition, which is affected by the balance between evaporation and precipitation and temperature at the time of formation
- Unknown fractionation processes, which can include evaporation in petroleum reservoirs above ~80°C.
- Contamination by fracturing fluids.
Clayton R.N., Friedman I., Graf D.L., Mayeda T.K., Meents W.F., Shimp N.F. (1966) The origin of saline formation waters: 1. Isotopic composition. Journal of Geophysical Research 71, 3869–3882.
Ferronsky V.I., Polyakov V.A. (2012) Isotopic composition of formation waters. In: Isotopes of the Earth’s Hydrosphere. Springer, Dordrecht.