下扬子皖南地区下寒武统大陈岭组页岩特征及其沉积环境

下扬子皖南地区下寒武统大陈岭组发育富有机质页岩，前期对该套页岩的关注和研究较为薄弱。为探索大陈岭组页岩特征及其沉积环境，以该区页岩气探井WY1井为研究对象，基于岩心、测井资料，通过全岩X射线衍射、氩离子抛光扫描电镜、有机地球化学、元素地球化学等测试手段，重点分析页岩岩石矿物组成特征、有机地球化学特征、孔隙特征，讨论其沉积环境。结果表明：大陈岭组页岩矿物组成以石英、黏土矿物为主，为生物成因硅质页岩，过量硅含量为33.77%～61.79%，占总硅质含量的46%～75%；页岩有机质丰度高，TOC分布在2.27%～7.42%之间，平均值为4.06%，等效镜质体反射率（Ro,eqv）为3.37％～5.53％，均处于过成熟演化阶段，有机质严重碳化，测井电阻率普遍低于1 ?·m；发育无机孔隙、有机质孔隙和微裂缝3种孔隙空间类型，有机质孔隙较发育，但主要为孔径10～20 nm的小孔，有效孔隙度平均为1.25%；大陈岭组形成于深海至滞流浅海，自下而上水体滞留程度增强，整体处于贫氧—厌氧的古水体环境，沉积期气候温暖湿润，古生物繁盛，古生产力较高，生物Ba含量为1 738.15～5 687.74 ug/g，平均值为3 309.63 ug/g，沉积环境有利于有机质的富集保存；皖南地区大陈岭组富有机质页岩发育，具备页岩气形成的基本条件，深化过热演化程度页岩气富集主控因素研究，评价优选保存条件较好的稳定区，有望实现勘探新突破。

Characteristics and Sedimentary environment of the Lower Cambrian Dachenling Formation shale in the southern Anhui of Lower Yangtze area

The Lower Cambrian Dachenling Formation is a organic rich shale series in the southern Anhui of Lower Yangtze area,which has had less attention and study in the early stage.In order to explore the shale geologic characteristics and sedimentary environment of the Dachenling Formation,the geological conditions in the Dachenling Formation shale are analyzed using data from cores,well logging,and lab test results from the well WY1,including the sedimentary characteristics,rock minerals composition,organic geochemical characteristics,and pore characteristics of the Dachenling Formation.The results show that the shale mineral composition of the Dachenling Formation is mainly quartz and clay minerals,which is biogenic siliceous shale.The excess silicon content is 33.77%-61.79%,accounting for 46%-75% of the total siliceous content;Shale has high organic matter abundance,TOC is distributed between 2.27%-7.42%,the average value is 4.06%,and the equivalent vitrinite reflectance (Ro,eqv) ranged from 3.37% to 5.53%.They are in the stage of over mature evolution,the organic matter is seriously carbonized,and the logging resistivity is generally lower than 1 ?·m;There are three types of pore space: inorganic pores,organic pores and micro fractures.The pores of organic matter are relatively developed,but they are mainly small pores with a pore diameter of 10-20 nm,and the average effective porosity is 1.25%.The Dachenling Formation was deposited in deep sea to stagnant shallow sea,and the retention degree of water body increased from bottom to top.It was generally in an oxygen poor anaerobic paleowater environment.During the sedimentary period,the climate was warm and hu-mid,paleontology was prosperous,paleoproductivity was high,and the biological Ba content was 1 738.15-5 687.74 ug/g,with an average value of 3 309.63 ug/g.The sedimetary environment was conducive to the enrichment and preservation of organic matter.The Dachenling Formation is rich in organic shale in the southern Anhui,which has the basic conditions for the formation of shale gas.It is expected to achieve a new breakthrough in exploration by deepening the research on the main controlling factors of shale gas enrichment in the degree of overheating evolution,evaluating and optimizing stable areas with good preservation conditions.