湖北鹤峰地区二叠系大隆组黑色岩系特征及成因初探

Characteristics and preliminary study on genesis of black rock series of Upper Permian Dalong Formation in Hefeng area,Hubei Province

根据6条露头剖面和HD1井的详细观测,通过借助偏光显微镜、X-射线衍射、场发射扫描电镜和有机碳含量(TOC)分析等对鹤峰地区二叠系大隆组黑色岩系的岩石学和矿物学特征进行了研究。岩石类型总体呈现泥页岩局部夹碳酸盐岩和薄层状硅岩的特征,有机质含量较高,有利于后期成岩流体的改造和页岩气开发阶段的水力压裂改造。垂向上,大隆组可划分为6个岩性段,反映出沉积水体呈深→浅→深→浅的变化特征。矿物组分以硅质为主,主要具有生物成因和次生成因的类型,碎屑成因类型较少。矿物、岩石特征分析表明,大隆组黑色岩系的形成主要是受被碳酸盐台地三面围限的滞留的台盆相缺氧还原环境的控制,同时沉积过程中受到上升流作用以及与同生断裂作用有关的热水的影响。

According to detailed observation of the 6 outcrop sections and Well HD1, and in combination with polarizing microscope,X-ray diffraction （XRD）,field emission scanning electron microscopy （SEM） and organic carbon content （TOC） analysis, the petrological and mineralogical characteristics of black rock series of Upper Permian Dalong Formation in Hefeng area,Hubei Province,is studied.There are three rock types of shale, carbonate and silica rock in Dalong Formation which has high content of organic matter and is composed of black rock series.Shale is the main rock type,carbonate and silica rock are as thin layers a- mong shale.The petrological characteristics of black rock series is advantageous to the influence of late dia- genetic fluid and the formation of hydraulic fracturing in the shale gas development phase.It can be divided into 6 lithology sections in vertical of Dalong Formation,which reflect the sedimentary water body had ex- perienced twice deep-to-shallow evolution processes.Quartz as the main mineral, is dominated by biogenesis and diagenesis type,however,clastogene is the least type.The formation of black rock series in Dalong For- mation is mainly affected by oxygen reduction environment in platform basin facies, which is influenced by the retention of the carbonate platform in the circle of platform shelf on three sides, meanwhile is also pos- sibly influenced by upwelling action in deposition process, and also the hot water should be considered, which related to the syngenetic faulting.