富有机质页岩和石油中马来酰亚胺类化合物的分布与意义

Distribution and significance of maleimides in organic matter-enriched shales and derived crude oils

马来酰亚胺或1H-吡咯-2,5-二酮来源于叶绿素或细菌叶绿素的降解,是沉积有机质和石油中一类新型生物标志化合物。通过对国内外几个含油气盆地富有机质页岩的可溶有机质(EOM)和原油进行精细分离,在目标馏分F2中发现了丰富的马来酰亚胺类化合物,尤其是主要由光合绿硫细菌生成的2-甲基-3-异丁基(Me,i-Bu)和2-甲基-3-正丙基(Me,n-Pr)马来酰亚胺。研究表明,2-甲基-3-异丁基和2-甲基-3-正丙基马来酰亚胺在海相和咸化湖盆中十分发育,表明透光滞水带(PZE)发生在松辽盆地嫩江组微咸水环境、渤海湾盆地沙河街组咸水—半咸水环境和奥连特盆地Napo组海相环境,指示强还原的保存条件。北部湾盆地2-甲基-3-异丁基和2-甲基-3-正丙基马来酰亚胺的出现反映流沙港组二段油页岩形成过程中存在PZE,同样反映还原环境以及微咸水水体。可见,PZE是有机质富集和优质烃源层发育的有利因素。进一步分析发现,(Me,i-Bu)/(Me,Et)(甲基,乙基)和(Me,n-Pr)/(Me,Et)参数可以区分海相、半咸水—咸水湖相和微咸水湖相环境。

The maleimides,or 1H-pyrrole-2,5-diones,are one of the novel types of biological markers existed in both sedimentary organic matter and petroleum,which could be products derived from the degradation of chlorophylls and bacteriochlorophylls.In this study,the maleimides composition was investigated in detail for several crude oils and petroleum source rocks with varying depositional settings,and abundant 2-methyl-3-n-propyl(Me,n-Pr)and 2-methyl-3-isobutyl(Me,i-Bu)maleimide,together with aryl isoprenoids were detected.These pigments-derived products were prominently generated by Chlorobiaceae and are especially abundant in the saline and marine black shales and related oils,indicating that PZE(photic zone euxinia)occurred in the brackish water environment of the Nenjiang Formation in the Songliao Basin,the saline to semi-saline water environment of the Shahejie Formation in the Bohai Bay Basin,and the marine environment of the Napo Formation in the Oriente Basin,showing strong reduction preservation conditions.It can be concluded that PZE is a favorable factor for the enrichment of organic matter and the development of high-quality source layers.In addition,the ratios of Me,i-Bu/Me,Et and Me,n-Pr/Me,when coupled together,could be used to diagnose the depositional conditions such as marine,saline,semi-saline or brackish water column.