Pyrolysis of one crude oil and its asphaltenes: Evolution of gaseous hydrocarbons and carbon isotope

Pyrolysis was carried out in anhydrous closed system (gold tubes) under a constant pressure of 50 MPa to discuss the differences of gas generation mechanism between crude oil and its asphaltenes. Yields and carbon isotopic composition of gaseous hydrocarbons were determined. The results show that the yield curves of gaseous hydrocarbons generated from crude oil have analogy change trends with that of asphaltenes correspondingly. The yield of methane generated from asphaltene cracking is 50% of that of oil cracking when oil and asphaltene cracked completely. The relation of δ13C1 < δ13C2 < δ13C3 exists in the whole process of pyrolysis, and the δ13C value of methane, ethane and propane generated from oil is more than that of asphaltene correspondingly. Kinetic parameters of gaseous hydrocarbon generation for crude oil and asphaltene were obtained by kinetic calculation, and the result can be extrapolated to geological conditions.