Laser-Raman spectroscopy characteristics of natural gas hydrates from Qilian Mountain permafrost

Natural gas hydrates recovered from the Juhugeng ore district in the Muli coalfield of the Qilian Mountain were investigated by micro-Raman spectroscopy at 77K and ambient pressure,and the representative Raman spectra of the natural gas hydrates in the permafrost were obtained.The measurements prove the existence of hydrates at the depths of 133.30m,139.52~139.92m and 141.00m in the hole of DK3.Based on a detailed analysis of the Raman spectra and consulting the literatures available,the authors preliminarily judge that all of the hydrates at three different depths are of sⅡ.Furthermore,the spectral lines of different gas molecules trapped in the hydrates were identified by their characteristic vibration signatures,and the approximate components of the guest gases were determined.