下扬子地区高家边组底部黑色页岩与北美Marcellus页岩地质特征对比

从地层形成的构造古地理环境、地层的厚度及空间展布以及烃源岩的岩性特征等方面,对美国东部阿巴拉契亚盆地中泥盆统Marcellus页岩和下扬子地区的下志留统高家边组黑色页岩作对比研究。结果发现,两套地层形成于相似的古地理环境,都沉积于前陆盆地早期缺氧的闭塞水体中,都是有利于细粒的有机质保存形成黑色页岩的环境。两套地层的分布和埋深都受到同沉积构造及其后期改造作用的相互影响,同时也对其中页岩的空间分布和勘探前景起重要的控制作用。两套页岩都是较好的烃源岩,含有较高的总有机碳(TOC)和脆性矿物,且都达到了高成熟阶段,生气和产气潜力大。相对于Marcellus页岩,高家边组黑色页岩TOC含量较低,埋深更大,而且受到多次构造作用的改造,使得其勘探风险相对较大。

Geological Comparison of Silurian Gaojiabian Formation of Lower Yangtze Area and Middle Devonian Marcellus Formation in the Appalachian Basin in North America

Based on paleogeography and tectonic settings, strata spatial distribution characteristics, basic geochemistry indexes and mineral composition, we compared lower part of Lower Silurian Gaojiabian Formation of Lower Yangtze area and middle Devonian Marcellus Formation in the Appalachian basin. The results show that the two sets of shales shared similar paleogeography and tectonic settings, both accumulated in tranquil anoxic basinal waters and their euxinic depositional site allowed the preservation of the finely organic detritus. The stratigraphy and thickness trends of both formations reflect the interplay of tectonism during the formation time and the later stage. These events shaped the stratigraphic architecture of both formations and can impact the exploration and production strategies of shale gas. Both formations are considered to be good source rocks for the exploration of shale gas and they both have high thermal maturity and contain relatively high total organic carbon (TOC) content, as well as large amount of brittle minerals. Compared with Marcellus shale, Gaojiabian Formation contains less TOC content, has a deeper burial depth burial depth and has been reworked by multicycle tectonism, which bring higher risks for the exploration of shale gas.