裂解热模拟实验中碳同位素变化特征及其地球化学意义

采用高温模拟技术，对原油、氯仿沥青“A”、烃源岩、干酪根和原油族组分样品进行热模拟实验，分析不同样品在裂解过程中产物碳同位素组成的变化特征，研究其地球化学意义。原油、氯仿沥青“A”、干酪根、烃源岩和饱和原油族组分随热演化温度的增加，热模拟气态烃碳同位素演化规律是由重变轻再变重的演化趋势，700℃以前碳同位素分布呈正碳同位素系列分布，750℃以后出现丙烷碳同位素倒转，芳烃馏分和沥青质馏分的碳同位素值和正碳同位素系列分布出现差异；各样品随热模拟温度的增加，Δδ¹³C_2-1值都呈增大的趋势；Δδ¹³C_3-1、Δδ¹³C_3-2对原油、氯仿沥青“A”、饱和烃馏分与芳烃馏分和沥青质馏分随模拟温度的变化有差异；δ¹³C₂ -δ¹³C₃ 值和LN（C₂/C₃）值随模拟温度的增加呈正相关性。

Stable Carbon Isotope Compositions of Gaseous Hydrocarbons in Pyrolysis Experiment and Geochemical Significance

In this paper,different types of samples,including crude oil,chloroform bitumen A,oil fractions (saturated hydrocarbon,aromatic hydrocarbon and asphaltene),source rock and kerogen,were performed in pyrolysis experiment at high temperature.Carbon isotope composition of gaseous hydrocarbons was measured.With increase of pyrolysis temperatures,δ¹³C values of gaseous hydrocarbons from different types of samples (i.e crude oil,chloroform bitumen A,kerogen,source rock,and saturated hydrocarbon) were various,with heavy value of ¹³C at low temperature,lighter value at moderate temperature,and heavier value at higher pyrolysis temperature.A normal serial of stable carbon isotopes for methane,ethane and propane occurred before pyrolysis temperature less than 700℃.But,reverse trend happened at pyrolysis temperature more than 750℃.The different change of stable carbon isotope values and normal serial for gaseous hydrocarbons from aromatic hydrocarbon and asphaltene existed.Δδ¹³C_2-1 values for gaseous hydrocarbon from all samples increased with pyrolysis temperature increasing.Values of Δδ¹³C_3-1and Δδ¹³C_3-2 were various for samples.A position correlation between δ¹³C₂-δ¹³C₃ and Ln（C₂/C₃）occurred with pyrolysis temperature increasing.