油气田水中氢氧同位素分析新技术及应用

A new method for analysis of δ^(18)O and δD in oil-and-gas field water and its application

采用元素仪—同位素质谱计联机装置(EA-IRMS)对油气田水中氢氧同位素组成进行在线分析。样品水在高温(1 450℃)裂解炉内与玻璃碳粒反应生成H2和CO,经过色谱分离,并被载气带入质谱计。根据二者不同的保留时间,设定磁场转换,依次测定氢氧的同位素组成。该方法一次进样即能完成氢氧同位素的测定,效率高、重复性好。将该方法应用于四川盆地天然气田水样的分析,结果显示三叠系须家河组地层水可能存在古代大气降水和海源沉积水的掺和。

We described a new and simple on-line pyrolysis method for the analysis of δ18O and δD in oil-and-gas field water by continuous flow EAqRMS. The sample water was converted into CO and H2 in glassy carbon tube which was filled with glassy carbon granules at high temperature （1 450℃）. And then, CO and H2 were separated in GC column prior to transferring into the ion source of the Isotope Ratio MS for sequential determination of hydrogen and oxygen isotopes of the sample by magnet switching. This method performed dual measurements of δ18O and SD from a single sample, and had high efficiency and good productivity. Using this method, we measured some water samples from gas fields in the Sichuan Basin. The results showed that the water of Triassic Xujiahe Formation was the mixture of marine sedimentary and ancient meteoric water.