湘中拗陷海相页岩层系岩相古地理特征

湘中拗陷是一个以下古生界浅变质岩系为基底发展起来的晚古生代沉积拗陷区,发育有机质丰度高的海相页岩层系,具有形成页岩气藏的基本地质条件。以现代沉积学和层序地层学理论为指导,结合湘中拗陷区域构造背景,分析页岩层系沉积环境,恢复页岩层系的岩相古地理,确定富有机质页岩层系发育层段。湘中拗陷的泥页岩主要发育于下石炭统及中上泥盆统和上二叠统,分布在海侵体系域上部和高水位体系域下部,平面上多与凹槽台地相的发育和分布有关。最有利于泥页岩发育的主要沉积相带是台地海盆相和滨海(海湾)沼泽相。

Lithofacies-paleogeography characteristics of the marine shale series of strata in the Xiangzhong depression, Hunan, China

The Xiangzhong depression is a late Paleozoic sag region developing based on the Lower Paleozoic epimetamorphic rock series.The marine shale series of beds are abundent in organic matter and provides basic geological conditions for forming shale-gas reservoirs.Under the guidance of modern sedimentology and sequence stratigraphy and combined with the regional tectonic setting of the Xiangzhong depression,this study analyzes the depositional environment and lithofacies-paleogeography of the shale series of strata,ascertains the developed shale intervals rich in organic matter and suggests that the shale in the Xiangzhong depression mainly develops in Lower Carboniferous,Middle-Upper Devonian and Upper Permian.The shale is distributed on the top of the transgressive system tract and on the bottom of the highstand system tract and the better shale is laterally relative to the development and distribution of trough rock platform facies.The most advantageous sedimentary facies for the development of the shale are the platform basin facies and seamarsh facies.