梁平福禄镇剖面大安寨段泥页岩地质特征

Geological characteristics of mud shale in Da’anzhai section of Fulu Town,Liangping

四川盆地侏罗系湖相泥页岩具有沉积相变快、岩性组合类型复杂多样、储层非均质性强的特点,与海相页岩存在较大的差异,因此,建立湖相泥页岩典型地质剖面,深入研究微相及岩性组合特征具有重要意义。选取川东重庆市梁平区福禄镇剖面大安寨段作为研究对象,通过对小层划分、沉积微相及其岩性组合特征的精细描述、样品采集,以及有机地化、储层物性和全岩X衍射等测试分析,结果表明:福禄镇剖面大安寨段主要为碳酸盐岩湖泊沉积,经历了完整的初始湖侵—最大湖侵—初始湖退3个阶段,微相及岩性组合具明显的三段式。大一亚段和大三亚段主要以碳酸盐浅湖介屑滩微相沉积的厚层介屑灰岩为特征,大二亚段为半深湖沉积,发育了湖坡风暴滩和半深湖泥2个微相,分别以灰色介屑灰岩与灰黑色泥页岩不等厚互层和厚层黑色页岩夹薄层介壳灰岩2种岩性组合为特征,泥页岩厚度大、有机质含量较高,特别是页岩与介屑灰岩互层组合,有利于微裂隙发育,脆性矿物含量相对较高,具有更好的渗透性和可压性,是页岩油气富集的甜点层段。与四川盆地典型页岩气钻井对比:大二亚段半深湖相主要分布于川东涪陵—建南地区,有利于页岩油气的形成;大一亚段和大三亚段碳酸盐浅湖介屑滩主要分布于川中—川东北地区,有利于致密油气的富集。

The lacustrine mud shale in Jurassic of Sichuan Basin is characterized by fast sedimentary phase transition,complex and diverse lithological combination types,and strong reservoir inhomogeneity,which is quite different from the marine shale.Therefore,it is of great significance to establish a typical geological section of Jurassic lacustrine shale in Sichuan Basin and further study the microfacies and lithologic assemblage characteristics of lacustrine shale.The Da’anzhai section of Fulu Town,Liangping District,Chongqing,Eastern Sichuan is selected as the research object.Through the division of small layers,fine description of sedimentary microfacies and lithologic combination characteristics,sample collection,field profile measurement,organic geochemistry,reservoir physical properties and whole rock X-ray diffraction,it is shown that the Da’anzhai section of Fulu town is mainly carbonate lake sediments.The microfacies and lithologic assemblages have three stages:initial transgression,maximum transgression and initial regression.The first and third members of the Da’anzhai formation are mainly composed of the microfacies of the thick layer mesoclastic limestone deposited in the bioclastic beaches of the carbonate shallow lake;The second member of Da’anzhai formation is a semi deep lacustrine subfacies.There are two microfacies:Storm beach and semi deep lacustrine mud.They are characterized by two lithologic associations,i.e.unequal thickness interbedding of grey clastic limestone and grey black shale,and thick black shale with thin shell limestone,With high content of brittle minerals and better permeability and compressibility,it is a sweet spot for shale oil and gas enrichment.Compared with the typical shale gas drilling,The semi deep lacustrine facies of the second member is mainly distributed in Fuling Jiannan area in eastern Sichuan,which is conducive to the formation of shale oil and gas.The carbonate shallow lacustrine clastic shoals of the first and third members are mainly distributed in Central Sichuan Northeast Sichuan,which is conducive to the enrichment of tight oil and gas.