四川威远及云南昭通区块龙马溪组优质页岩组构差异性与矿物纳米力学特征  

Fabric difference and mineral nanomechanics characteristics of high-quality shale in Longmaxi Formation, Weiyuan block in Sichuan Basin and Zhaotong block in Yunnan Province

作　　者：杨恒林 张俊杰 王高成 付利 孙清华 田中兰 Yang Henglin;Zhang Junjie;Wang Gaocheng;Fu Li;Sun Qinghua;Tian Zhonglan(CNPC Drilling Research Institute,Beijing 102206,China;PetroChina Zhejiang Oilfield Company,Hangzhou,Zhejiang 310023,China)

机构地区：[1]中国石油集团钻井工程技术研究院 [2]中国石油浙江油田公司

出　　处：《天然气勘探与开发》2018年第1期16-22,共7页Natural Gas Exploration and Development

基　　金：国家科技重大专项"工厂化钻井关键技术研究与应用"(编号:2016ZX05022-001);"昭通页岩气勘探开发示范工程"(编号:2017ZX05063)

摘　　要：四川威远及云南邵通区块志留系下统龙马溪组龙一~1亚段富有机质黑色页岩是页岩气开发的主要目的层,评价其可压裂性即可知其储层的可改造性。通过X射线衍射、扫描电子显微镜和纳米压入技术分别获取了龙一~1亚段矿物组分含量、胶结结构以及不同矿物弹性模量,揭示其脆性特征差异性,并分析了页岩中黏土矿物含量以及胶结类型对页岩裂缝非稳态扩展的影响机理。结果表明:(1)龙一~1亚段黏土矿物含量自上而下逐渐降低,脆性逐渐增强;(2)胶结类型由黏土矿物基底胶结结构逐渐演变为硅质等颗粒支撑结构;(3)页岩中硅质和有机质弹性模量分别为78.4~91.8 GPa和6.1~9.3 GPa。结论认为:(1)页岩基质脆性可以视为压裂过程中页岩裂缝具有发生非稳态扩展的能力,龙一_1~1和龙一_2~1层页岩黏土矿物含量质量分数低于30%,胶结类型为颗粒支撑结构,压裂过程中裂缝发生非稳态扩展,易产生网状裂缝;(2)页岩的黏土矿物含量和石英等矿物颗粒支撑结构控制裂缝稳态—非稳态扩展,龙一_4~1层黏土矿物含量质量分数高于40%,大排量压裂过程中裂缝易沿着层理面稳态延伸。L11,organic-rich black shales of the Lower Silurian Longmaxi Formation,Weiyuan block in Sichuan Basin and Zhaotong block in Yunnan Province,is the main target layer for developing shale gas in southern Sichuan Basin.So,it is necessary to identify its fracturability.In this paper,the mineral composition,cementation structure,and elastic modulus were figured out by X-ray diffraction(XRD),scanning electron microscope(SEM)and nanoindentation technology(NIT),in order to reveal the diversity of brittleness characteristics.Moreover,the content of clay minerals and the influential mechanisms of cementation types on the unsteady propagation of shale fractures were analyzed.Results show that:(1)the content of clay minerals decreases whereas the brittleness increases,from top to bottom;(2)the cementation type is evolved gradually from the cementation structure with clay minerals as the basement to the one with the silica and other particles as the support;and(3)the elastic modulus of silica and organic matter are 78.4–91.8 GPa and 6.1–9.3 GPa,respectively.As concluded,shale fractures have the capability of unsteady propagation during fracturing due to brittleness of shale matrix.The mass fraction of clay mineral content is less than 30%in L11 1 and L11 2 shales,and the cementation is of particle support structure,so unsteady propagation of induced fractures and fracture networks tend to be formed easily.Moreover,the steady–unsteady propagation of fractures is controlled by the content of clay minerals and the support structure of mineral particles(e.g.quartz).The mass fraction is more than 40%in L11 4 shale,so the fractures tend to propagate steadily along bedding plane in the process of fracturing at high flow rate.

关 键 词：早志留世 优质页岩 组构差异性 矿物组分 胶结结构 弹性模量 

分 类 号：P618.13[天文地球—矿床学]