黔中隆起北部上奥陶统-下志留统页岩特征

Features of the shale from Upper Ordovician-Lower Silurian in the north of Middle Guizhou uplift,China

探讨黔中隆起北部五峰组-龙马溪组黑色页岩沉积特征。通过野外露头及结合前人资料,分析表明研究区上奥陶统五峰组、下志留统龙马溪组沉积环境为浅水陆棚与深水陆棚的交替:五峰组黑色页岩段为深水陆棚;五峰组观音桥段为浅水陆棚;龙马溪组黑色页岩段为深水陆棚;龙马溪组泥岩-灰岩段为浅水陆棚。沉积环境的明显差异直接导致五峰组和龙马溪组黑色页岩主要有机地化参数(如TOC)的不同,TOC质量分数较高的黑色页岩段集中在五峰组下段与龙马溪组下段,为页岩气发育的有利层段。

This paper discusses the sedimentary features of the black shale in Wufeng-Longmaxi Formation in the north of Middle Guizhou uplift. Analysis of the outcrops and the predecessors＇ materials shows that in the upper Yangtze area, the sedimentary environments of Upper Ordovician Wufeng Formation and Lower Silurian Longmaxi Formation are the shallow shelf and deep water shelf alternatively. The black shale of Wufeng Formation is deep-water shelf, the Guanyinqiao segment of Wufeng Formation is shallow shelf, the black shale of Longmaxi Formation is deep-water shelf and the mudstone-limestone of Longmaxi Formation is shallow shelf. The obvious differences of the sedimentary environments directly lead to the differences of the main organic geochemical parameters, such as TOC of the black shale. The black shale with high TOC content concentrate in the bottom segments of Wufeng Formation and Longmaxi Formation which are the best segments for generating shale gas.