摘要
Gaseous hydrocarbon geochemistry research through a thermal simulation experiment in combination with the natural evolution process in which natural gases were formed from coal-measure source rocks revealed that the {δ{}+{13}C-1} values of methane vary from light to heavy along with the increase of thermal evolution degree of coal-measure source rocks, and the {δ{}+{13}C-2} values of ethane range from {-28.3‰} to {-20‰} (PDB). {δ{}+{13}C-2} value was {-28‰±} (R-O={0.45%}-{0.65%}) at the lower thermal evolution stage of coal-measure source rocks. After the rocks entered the main hydrocarbon-generating stage (R-O={0.65%}-{1.50%}), {δ{}+{13}C-2} values generally varied within the range of {-26‰}-{-23‰±}; with further thermal evolution of the rocks the carbon isotopes of ethane became heavier and heavier, but generally less than -20‰.; The partial carbon isotope sequence inversion of hydrogen gases is a characteristic feature of mixing of natural gases of different origins. Under the condition of specially designated type of organic matter, hydrogen source rocks may show this phenomenon via their own evolution.; In the lower evolution stages of the rocks, it is mainly determined by organic precursors that gaseous hydrocarbons display partial inversion of the carbon isotope sequence and the carbon isotopic values of ethane are relatively low. These characteristic features also are related to the geochemical composition of primary soluble organic matter.
Gaseous hydrocarbon geochemistry research through a thermal simulation experiment in combination with the natural evolution process in which natural gases were formed from coal-measure source rocks revealed that the δ^ 13 C1 values of methane vary from light to heavy along with the increase of thermal evolution degree of coal-measure source rocks, and the δ^13 C2 values of ethane range from -28.3‰ to - 20‰ （PDB）. δ ^13 C2 value was - 28 ‰ ± （ Ro = 0.45% - 0.65% ） at the lower thermal evolution stage of coal-measure source rocks. After the rocks entered the main hydrocarbon-generating stage （Ro = 0.65% -1.50% ） , δ ^13C2 values generally varied within the range of -26‰ - -23‰ ± ; with further thermal evolution of the rocks the carbon isotopes of ethane became heavier and heavier, but generally less than - 20‰. The partial carbon isotope sequence inversion of hydrogen gases is a characteristic feature of mixing of natural gases of different origins. Under the condition of specially designated type of organic matter, hydrogen source rocks may show this phenomenon via their own evolution. In the lower evolution stages of the rocks, it is mainly determined by organic precursors that gaseous hydrocarbons display partial inversion of the carbon isotope sequence and the carbon isotopic values of ethane are relatively low. These characteristic features also are related to the geochemical composition of primary soluble organic matter.
基金
This research projectwas financiallysupported jointlybythe National Bas-ic Research (973) Programof China (No.2001CB209102) and the ImportantDirection Project of Knowledge Innovation in Resources and EnvironmentField sponsored by the Chinese Academy of Sciences (KZCX3-SW-128).
关键词
煤资源
热量模拟
碳
同位素
coal-measure source rock
thermal simulation
carbon isotope
