黔北绥阳地区五峰—龙马溪组富有机质泥岩特征及意义

Characteristics of organic-rich shale in Wufeng-Longmaxi formations in Suiyang area of northern Guizhou and its implication to shale gas

黔北地区五峰—龙马溪组富有机质泥岩由黔北隆起向南厚度逐渐增大,沉积相分别由潮坪、浅水陆棚、深水陆棚组成。黔北绥阳地区枧坝剖面黑色泥岩厚度达33.1 m,沉积序列与黔北其他剖面具有一致性,但是与周边剖面相比其厚度明显增大,表明该区发育棚内洼地深水陆棚相沉积。枧坝剖面五峰—龙马溪组泥岩段有机碳含量在0.53%~6.04%之间,平均3.05%,热解峰温一般大于500℃,镜质体反射率处于1.93%~2.19%之间,平均为2.07%,热演化程度总体处于过成熟阶段;其脆性矿物平均含量70.5%,黏土矿物平均含量29.5%,具有高含脆性矿物特征。黔北绥阳地区具有良好的页岩气基本地质条件。

The organic-rich shale in the Wufeng-Longmaxi formations in the northern Guizhou was deposited in tide flat,shallow or deep continental seas,respectively,with an increasing thickness from north to south.The black shale in the Jianba section in the Suiyang area of the northern Guizhou has a thickness of 33.1 m,which is obviously thicker than the other sections even though they have similar sedimentary sequences,indicating for a sedimentary depression in this area.Organic carbon content in the Wufeng-Longmaxi formations ranges from 0.53%to 6.04%,with an average value of 3.05%.The T max is generally higher than 500℃.The R o ranges from 1.93%to 2.19%,with an average value of 2.07%,indicating for an over-mature stage.Brittle mineral content is high across the section,accounting for 70.5%in average.The discovery of the Jianba section sheds new light on shale gas exploration in the northern Guizhou.