Determination of carbon isotopic composition of individual light hydrocarbons evolved from pyrolysis of source rocks by using GC-IRMS

The carbon isotopic composition of individual light hydrocarbons generated from source rocks that had been pyrolysed in vacuum glass tube were determi ned by using the GC-IRMS techniques. The results indicate that abundant CO2 in the pyrolysates has a remarkable effect on the determination of CH(4)de lta(13)C. Running cryogenically with an initial temperature of -40 degrees C can effectively eliminate the effect. In addition, it conduces to measuri ng the delta(13)C Of C2+ hydrocarbons by increasing the injection volume an d/or absorbing CO2 with the solution of sodium hydroxide. The above measure s will help to get the carbon isotopic composition of C-1-C-7 components, w hich is of great significance for gas/source rock correlation and for study on the genesis of natural gas.