南盘江盆地泥盆系沉积体系及页岩气远景区带

DEVONIAN SEDIMENTARY SYSTEM AND SHALE-GAS PROSPECTING ZONE OF NANPANJIANG BASIN

文章综合利用实测重点剖面资料、区域地质调查资料,结合已经公开发表的成果,讨论了南盘江盆地泥盆系沉积体系类型、特征及其分布规律,基于深水细粒沉积相带的分布,预测了南盘江盆地泥盆系页岩气远景区带。南盘江盆地泥盆系发育河流三角洲—陆源碎屑滨岸、陆源碎屑内陆架、陆源碎屑外陆架、局限台地、开阔台地、台地边缘、陆坡及深海8种沉积体系。早泥盆世,最初,除南部钦防地区外,南盘江盆地大部分地区无沉积,随后海水自南而北入侵,形成了广泛分布的河流三角洲—陆源碎屑滨岸体系沉积。中泥盆世,古陆暴露范围显著缩小,陆源碎屑供应显著减弱,河流三角洲—碎屑滨岸体系局限于古陆的周缘,深水沉积区显著扩大,在深水沉积区与河流三角洲—碎屑滨岸体系间是以碳酸盐岩为特色的广泛的局限/开阔台地型沉积。晚泥盆世,古陆暴露范围进一步缩小,陆源碎屑供应贫乏,河流三角洲—碎屑滨岸相主要局限于云开古陆的周缘,深水沉积区进一步扩大,在深水沉积区与古陆间是以碳酸盐岩为特色的局限/开阔台地型沉积。根据深水沉积体系的分布和埋藏条件,南丹、紫云、扶绥、广南等地区是寻找泥盆系页岩气最具远景的地区,永福—鹿寨—平乐—武宣地区是寻找泥盆系页岩气值得关注的地区。

Based on on-site cross sections,regional geology,publications,this paper discusses its sedimentary system types,features and distribution of Nanpanjiang basin,and forecasts the prospecting shale-gas zones on the basis of the distribution of deep water fine grained sedimentary facies. The Devonian in Nanpanjiang basin develops river delta, where holds eight sedimentary systems, continental debris offshore, continental debris inner shelf,continental debris outer shelf,restricted platform,open platform,platform margin,slope and deep sea. In the early Devonian,there is no sedimentation in most Nanpanjiang basin except the southern Qinfang area. The transgression northward forms a widely-spreading river delta,continental debris offshore sedimentary system. During the middle Devonian,the continental land diminishes with a decreased supply of continental source,river delta-debris offshoreonly distributes along the land margin as deep water sedimentation largely expands. Between them is widely-spreading constrained/open platform sedimentation, featured by carbonates. Entering the late Devonian, lands diminishes further,short of continental supply. River delta-debris offshore facies only distributes the margin of Yunkai continent,between them is also the carbonate-featured constrained/open platform sedimentation. According to the distribution and buried depth of deep water facies,Nandan,Ziyun,Fushui and Guangnan area are of shale gas potentials,also Yongfu-Luzhai-Pingle-Wuxuan area is worthy attention.