中上扬子地区埃隆阶最厚斑脱岩层分布特征及地质意义  

Distribution characteristics and geological significance of the thickest Aeronian bentonite bed in Middle-Upper Yangtze Region

作　　者：王玉满 李新景 陈波[2] 韩京[2] 张家铭[2] 袁飞[2] 马杰 代兵 王浩[2] 蒋珊 

机构地区：[1]中国石油集团科学技术研究院,北京100083 [2]长江大学,湖北武汉430100

出　　处：《天然气地球科学》2018年第1期42-54,共13页Natural Gas Geoscience

基　　金：中国科学院A类战略性先导科技专项(编号:XDA14010101);国家科技重大专项(编号:2017ZX05035001);中国石油勘探与生产分公司页岩气资源评价与战略选区课题(编号:101016kt1012001b24)联合资助

摘　　要：以野外露头和重点探井资料为基础,对中上扬子地区埃隆阶最厚斑脱岩层的分布特征及其在页岩气地质评价和"甜点层"预测中的独特作用进行了研究,初步获得3点认识:(1)埃隆阶最厚斑脱岩层在中上扬子地区大面积稳定分布,厚度为5~40cm,在大部分探区电性特征明显且易于识别,自然伽马值一般为188~235cps(或API),在川南、渝东等页岩气主要探区呈尖峰响应特征,在川中、川东北和中扬子等地区富有机质页岩段尖峰特征不明显或显低谷特征。(2)此斑脱岩层可以成为龙马溪组重点层段划分与区域对比的关键标志层。在野外和现场研究工作中,以此脱岩层为界向下搜寻半耙笔石的首现位置或其下方的首个伽马曲线低谷处,是确定鲁丹阶顶界的有效方法。(3)埃隆阶最厚斑脱岩层的出现,是扬子台盆区主体进入前陆挠曲强烈活动期和沉积速率显著加快期的重要标志,也是龙马溪组由富有机质、富硅质的岩相组合全面转向富黏土质岩相组合和富钙质岩相组合的沉积转折期,对五峰组—龙马溪组优质页岩的形成和分布具有重要控制作用。因此认为,该斑脱岩层出现以前是富有机质、富硅质页岩的主要形成期;在预测五峰组—龙马溪组"甜点层"空间展布时,必须考虑此斑脱岩层的控制作用;在中上扬子大部分地区,优质储层顶界的确定以不超过埃隆阶最厚斑脱岩层为宜。Based on the data from the outcrops and key exploratory wells,a basic analysis is provided to the distribution characteristics of the thickest bentonite layer of the Aeronian stage in Middle-Upper Yangtze Region and its unique role in the geological evaluation of shale gas and the prediction of＂sweet spot＂layer.Three preliminary conclusions have been reached：（1）The thickest bentonite layer of the Aeronian stage is widely and steadily distributed in the Middle-Upper Yangtze Region with a thickness of 5-40 cm,whose electric characteristics can be easily identified in most of the exploration areas.Gamma values of the bentonite layer are generally 188-235 cps（or API）.The gamma value peaks occur in southern Sichuan,eastern Sichuan and other primary shale gas exploration areas.On the contrary,in middle Sichuan,northeastern Sichuan and the north of Middle Yangtze Region,there is no gamma value peak or even the trough appears.（2）The bentonite layer can be considered as the key marker layer of the mainly segmental partition and the regional comparison of Longmaxi Formation.In the field,it is an effective way to determine the upper boundary of Rhuddanian,which can be found at the first appearance of the demirastrites and the first gamma curve trough.（3）The emergence of the thickest bentonite layer in the Aeronian stage has a profound influence on the formation and distribution of the high-quality shale of Wufeng-Longmaxi Formation.Its appearance is an important symbol for foreland basin folding and sedimentary rate increasing.Meanwhile,it also represents a transition in Longmaxi Formation from organic-rich and silica-rich shale to clay-rich and calcium-rich shale.Therefore,the organic-rich and silica-rich shales were mainly formed before the occurrence of the bentonite layer,and this control effect must be taken into account when predicting the spatial distribution of＂sweet spot＂layer in Wufeng-Longmaxi Formations.In most parts of the Middle-Upper Yangtze Region,the thickest bentonite layer in the

关 键 词：扬子地区 埃隆阶 斑脱岩 沉积响应 沉积速率 优质页岩 

分 类 号：TE122.2[石油与天然气工程—油气勘探]