四川盆地焦石坝构造区页岩有机质特征及其成烃能力探讨——以焦页1井五峰—龙马溪组为例

Characteristics and hydrocarbon significance of organic matter in shale from the Jiaoshiba structure,Sichuan Basin:A case study of the Wufeng-Longmaxi formations in well Jiaoye1

以四川盆地焦石坝构造区焦页1井为例,根据全岩、干酪根和微体化石等分析,对上奥陶统五峰组—下志留统龙马溪组富有机质泥页岩开展了成烃生物识别和有机岩石学研究,并对成烃能力进行了讨论。研究表明:高过成熟的五峰—龙马溪组页岩成烃生物主要由疑源类、藻类体(层状藻和底栖藻)和动物碎屑(笔石、几丁虫和海绵骨针)组成,成烃生物是有形态有机质的重要组成部分;无形态有机质是五峰—龙马溪组页岩有机质的主要组分,包括无定形体、微粒体和沥青,呈细小颗粒分散在矿物基质中。研究认为富氢的藻类体和笔石管胞内脂类大分子聚合物是主要的成烃母质,大量存在的无形态有机质,尤其是大量孔隙充填的细小固体沥青,说明原始生烃母质具有很强的生烃潜力,是形成页岩气藏的物质基础。

Organic-rich shale samples were collected from the Upper Ordovician Wufeng-Longmaxi formations in the Jiaoshiba structure in the Sichuan Basin to carry out rock, kerogen and micro-fossil analyses. The biological recognition and organic petrologic analysis of hydrocarbon generation were carried out, and the hydrocarbon po-tential was discussed. Hydrocarbon precursor organisms in the high-maturity or over-mature Wufeng-Longmaxi shale mainly included acritarchs, alginite （ lamalginite and benthic algae） and zooclasts （ graptolite, chitinozoan and spicule） , which were the major components of formed organic matter. However, amorphous organic matter was the primary portion in the Wufeng-Longmaxi shale, and was dispersed in the mineral matrix as fined parti-cles. Shale gas in Jiaoshiba area was derived from hydrogen-rich alginite and macromolecular lipid polymer in graptolite tracheids. Abundant amorphous organic matter, especially plenty of pore-filling fine-grained bitumen, indicated that the source rocks have high hydrocarbon potential, which could form large shale gas fields.