成熟——过成熟烃源岩有机质类型识别

Organic type identification for mature and postmature source rock

成熟—过成熟烃源岩有机质的氢指数和氧指数都极低,难以从氢指数—氧指数范式图中识别出其有机质类型。但是成熟—过成熟烃源岩有机质是由各种类型有机质相互组合形成的,据此发展了分布函数组合法来识别其类型。笔者首先推导了烃源岩有机质热演化过程的数学表征,然后利用此数学表征将未成熟—低成熟阶段各类型有机质的样本换算到成熟—过成熟阶段,据此估计了各类型有机质的氢指数(氧指数)分布函数,然后通过线性组合方法合成成熟—过成熟阶段有机质的氢指数(氧指数)的分布函数,最后根据组合系数得到成熟—过成熟阶段各类型有机质的占比,以识别成熟—过成熟阶段有机质类型。

Mature and postmature source rock has an extremely low hydrogen and oxygen index,so it is difficult to identify its organic type from a Van paradigm of hydrogen-oxygen index. Nevertheless,organic matter of mature and postmature source rock is formed by the combination of various types of organic matters. The authors developed a distribution function combination method to identify organic type in the mature and postmature stage. The authors first developed a math formula of thermal evolution process,and converted samples from mature and postmature stage to immature and low mature stage. Then the authors built distribution function and synthetic organic matter distribution function of the hydrogen/oxygen index by linear combination method in a mature and postmature stage,and finally determined the type of the organic matter by the linear combination weighting in a mature and postmature stage.