热演化过程中干酪根碳同位素组成的变化

VARIATION OF CARBON ISOTOPIC COMPOSITION OF KEROGEN DURING THERMAL EVOLUTION

熊永强 张海祖 耿安松

XIONG Yong-qiang ZHANG Hai-zu GENG An-song

中国科学院, 广州地球化学研究所, 有机地球化学国家重点实验室, 广东, 广州, 510640

State Key Laboratory of Organic Geochemistry, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou, Guangdong 510640, China

通过测定一个Ⅰ型干酪根在不同热演化阶段的残余率和残余部分的碳同位素组成,揭示其在热演化过程中的变化规律,从而为有效气源岩的定量判识与评价提供同位素方面的依据。研究表明,在产甲烷早期(Ro<1.5%),干酪根的碳同位素组成变化较明显,可达3.8‰;当Ro达到1.5%～2%时,随着热演化程度的增加,残余干酪根的δ13C略微呈现出逐渐贫13C的趋势,变化幅度约为2‰;当热演化程度较高(Ro>2%)时,干酪根的碳同位素组成则变化不大,变化幅度小于0.8‰。

Purpose of this study is to reveal the variation characteristics of kerogen during thermal evolution by determining the residual rate of kerogen and the carbon isotopic composition of residual kerogen at (different thermal) (evolution) stages, thus providing evidence of carbon isotope for quantitative identification and assessment of effective gas source rock. The result indicates that, at the early stage of methane (generation) (Ro1.5%), kerogen (obviously) enriches in 13C with the increasing of thermal evolution, up to 3.8‰. However, when Ro reaches 1.5%-2%, δ13C values of residual kerogen display a trend of slight depletion in 13C, varying within about 2‰. When the thermal maturity is higher (Ro2%), the variation of carbon isotopic composition is less than 0.8‰ for residual kerogen.

国家"十五"科技攻关项目(2001BA605A-04-04);中国科学院知识创新工程重大项目(KCZX1-SW-18-03).

https://doi.org/10.11781/sysydz200405484