Quantitative measurement of carbon isotopic composition in CO2 gas reservoir by Micro-Laser Raman spectroscopy

摘要

The use of Micro-laser Raman spectroscopy technology for quantitatively determining gas carbon isotope composition is presented. In this study, (CO2)-C-12 and (CO2)-C-13 were mixed with N-2 at various molar fraction ratios to obtain Raman quantification factors (F-12co2 and F-13co2). which provide a theoretical basis for calculating the delta C-13 value. And the corresponding values were 0.523 (0 C-12co2/C-N2 2) and 1.11998 (0 C-13co2/C-N2 1.5) respectively. It has shown that the representative Raman peak area can be used for the determination of delta C-13 values within the relative errors range of 0.076% to 1.154% in (CO2)-C-13/(CO2)-C-12 binary mixtures when F-12co2/F-13co2 is 0.466972625. In addition, measurement of delta C-13 values by Micro-Laser Raman analysis were carried out on natural CO2 gas from Shengli Oil-field at room temperature under different pressures. The delta C-13 values obtained by Micro-Laser Raman spectroscopy technology and Isotope Ratio Mass Spectrometry (IRMS) technology are in good agreement with each other, and the relative errors range of delta C-13 values is 1.232%-6.964%. This research provides a fundamental analysis tool for determining gas carbon isotope composition (delta C-13 values) quantitatively by using Micro-Laser Raman spectroscopy. Experiment of results demonstrates that this method has the potential for obtaining delta C-13 values in natural CO2 gas reservoirs. (C) 2018 Published by Elsevier B.V.