祁连山冻土区天然气水合物气体组分的气相色谱法测定

Gas chromatographic method for determination of gas composition from decomposed gas hydrate samples in Qilian Mountain permafrost

建立了气相色谱法测定祁连山冻土区天然气水合物C1-C5气体纽分的分析方法，对比研究了单点法与多点法校正、外标法与外标归一化法定量。以及顶空法与排水法2种气体收集方式的区别。结果表明：顶空法制备、单点法校正、外标归一化法定量计算为气相色谱法测定天然气水合物气体组分的最佳方法。方法相对标准偏差（ILSD）为0-1．06％，检出限为0．0003％-0．0127％。通过对祁连山冻土区DK一2孔10个天然气水合物样品的测定，发现C，含量为60．64％-78．76％，C：含量为8．99％-13．60％，C3含量为6．58％-21．24％，C4和C5含量较少，可见c，气体组分含量丰富，具有较低的C1／C2＋比值（1．5-3．7），显示出明显的热解气特征。关键词：祁连山冻土区；天然气水合物：气体组成；

In tbis paper, gas chromatographic method for determination of C1-C5 gas composition from decomposed gas hydrate sam- ples in Qilian Mountain permafrost was established, and the difference between single- and multi-point correction method, external standard and external standard normalization quantitative method, drainage and head space gas collection method was comparatively studied. The results indicate that the head space collection method, single correction method, and external standard normalization quantitative method are the best means for quantitatively measuring gas composition from the decomposed gas hydrate sample, with the relative standard deviations in the range of 0.10%-0.47%, and detection limits varying from 0.0003% to 0.0127%. Based on the deter- mination of C1-C5 from ten decomposed gas hydrate samples of bohehole DK-2 in Qilian Mountain permafrost, it is found that the content of C1 ranges from 60.64% to 78.76%, C2 from 8.99% to 13.60%, and C3 from 6.58% to 21.24%, with C4-C5 being less abun- dant. Gas hydrate in Qilian Mountain permafrost is enriched with C2＋ and has low C1/C~＋ ratios（ranging from 1.5 to 3.7）, showing the characteristics of thermogenic gases obviously.