Dissolved methane in water: temperature effect on Ramanquantification in fluid inclusions

This study confirms the ability of Raman spectroscopy for the quantification of methane in aqueous fluids trapped ininclusions. The procedure is based on the use of reference synthetic inclusions for calibration at various salinities. The temperature effect, which was suspected to be weak, has been confirmed using a natural metastable liquid inclusion. No temperature correction is needed between 80 and 175 °C. The Raman decomposition of the water stretching band using methane as an internal reference gives us the opportunity to follow the state of liquid water between 24 and 278 °C. The decrease of the hydrogen bonding contribution with temperature is responsible for the increase of the Raman CH4/H2O peak area ratio.