中国南方海相烃源岩中笔石生烃能力研究

摘要

The common development of graptolite in marine shale of Southern China has a close relationship with the formation of marine shale gas,but whether graptolite has hydrocarbon generating ability of shale gas has not been directly confirmed by relevant experiments.In this study,pure graptolite from black graptolite shale was selected and the graptolite sample was hand-picked for the experimental study on pyrolysis hydrocarbon generation.The results show that the graptolite is a good parent material.The carbon content of the graptolite is high,accounting for most carbon sources of graptolite shale.The main products of pyrolysis hydrocarbon generation are shale gas and light oil,which accounts for more than 94％ of the total hydrocarbon generation products,whereas the shale gas accounts for 54％.The pyrolysis product is similar to that between type-Ⅲ organic matter (OM) and type-Ⅱ OM is more similar to that of type-Ⅲ OM,which is mainly gaseous hydrocarbon products.The hydrocarbon generation ability of graptolite may be higher during thermal maturation process,which is closely related to the genesis of widespread shale gas in Southern China at present.%我国南方海相页岩中普遍发育的笔石与海相页岩气成因具有密切的关系,但笔石是否具有页岩气生烃能力,一直未有可靠的、直接的相关实验证实.本文通过采集笔石含量丰富的黑色页岩,手工挑选纯笔石样品并进行热解生烃模拟实验研究,证实了笔石页岩中的笔石是一种较好的生烃母质.笔石样品的碳含量较高,贡献了笔石页岩的大部分碳来源.达到生油高峰后的笔石热解生烃产物主要为天然气-轻质油,这两部分生烃产物占总生烃产物的94％以上,且其中的气态烃占总烃比例达到了54％左右.分析认为,笔石的热解生烃特征介于Ⅲ型有机质和Ⅱ型有机质之间,近似于Ⅲ型有机质生烃特征,以气态烃产物为主.由此推论,在笔石热成熟演化过程中,其有机质生烃能力可能更高,与目前南方广泛发育页岩气的成因息息相关.