页岩成岩裂缝形成机理及其主控因素

发布时间：2021-11-26 07:07

　　前人对干燥裂纹（龟裂缝）的形成机理和扩展规律进行了大量的研究。然而,富有机质页岩中成岩微裂缝的形成机制尚不清楚。根据研究建议,对海相、过渡相和陆相页岩样品的微裂缝进行了扫描电镜研究。同时,对页岩中常见的泥质矿物（蒙脱石、伊利石、高岭石）进行了实验研究,以确定干燥裂缝发育的主要控制因素,并探讨这些因素对裂缝几何形态的影响。页岩中普遍发育的成岩收缩裂缝与干燥裂缝具有明显的相似性。为模拟干燥裂缝的扩展过程,阐明收缩裂缝的形成机理,论文采用了成岩裂缝模拟机和实验室烘箱等进行了模拟试验,结果表明,粘土含量、温度和粘土层厚度是控制裂缝发生和发展的主要因素。裂缝宽度随层厚增加而增大,随着蒙脱石含量的增加而增大,但随着高岭石和伊利石含量的增加,裂缝宽度减小。对于某些单一成分的实验样品来说,当温度达到100℃和230℃时,干燥裂缝的数量将会进一步增加。混合样品则不存在这种现象。进一步,92%的干燥裂缝均呈现为三臂型,臂间夹角为90-100度和170-180度。脱水过程中的含水量在裂缝形成过程中起着重要作用,可分为四个阶段。大部分的裂缝都形成于初始和发展阶段,此时主要形成初始的单一裂缝并开始分叉。在自然界... 

【文章来源】：中国地质大学(北京)北京市 211工程院校 教育部直属院校

【文章页数】：155 页

【学位级别】：硕士

【文章目录】：
摘要
abstract
1 Preface
    1.1 Background and significance
        1.1.1 Background
        1.1.2 Significances
        1.1.3 Project supports
    1.2 Research status and existing problems
        1.2.1 Research status
        1.2.2 Existing problems
    1.3 Research content and technical ideas
        1.3.1 Research content
        1.3.2 Technical ideas
    1.4 Work completed
    1.5 Main achievements
2 The formation mechanism of diagenetic fractures of shale
    2.1 Characteristics and development patterns of desiccation cracks
        2.1.1 Basic characteristics of desiccation cracks
        2.1.2 Development patterns of desiccation cracks
        2.1.3 Geometrical parameters of desiccation cracks
    2.2 Formation mechanism of desiccation cracks
        2.2.1 Main mineral composition and characteristics of clays
        2.2.2 Mechanical condition for desiccation crack formation
        2.2.3 Stages of desiccation crack formation
        2.2.4 Main controlling factors of desiccation crack propagation
    2.3 Formation mechanism of shale diagenetic fractures and their distribution
        2.3.1 The model of formation processes from desiccation cracks to shale diagenetic cracks during diagenesis
        2.3.2 Analogy of formation mechanism and conditions of shale diagenetic fractures and clay desiccation fractures
        2.3.3.Formation mechanism of shale diagenetic fractures
3 Shale diagenesis
    3.1 Basic composition of shale
        3.1.1 Main mineral composition
        3.1.2 Organic matter composition of shale
        3.1.3 Fluids in shale
    3.2 Shale diagenesis
        3.2.1 Shale from marine facies
        3.2.2 Shale from transitional facies
        3.2.3 Shale from continental facies
    3.3 Main changes in shale diagenesis
        3.3.1 Under-compacted overpressure
        3.3.2 Cementation
        3.3.3 Mineral transformation
        3.3.4 Hydrocarbon generation
        3.3.5 Recrystallization
        3.3.6 Dehydration
4 Development mechanism of shale diagenetic fractures
    4.1 Main types of shale diagenetic fractures and their classification features
        4.1.1 Main types of shale diagenetic fractures
        4.1.2 Characteristics of shale diagenetic fractures
    4.2 Microfracture development mechanism
        4.2.1 Bedding cracks
        4.2.2 Stress tectonic cracks
        4.2.3 Shrinkage cracks
        4.2.4 Hydrocarbon generation cracks
        4.2.5 Undercompacted/ overpressure cracks
        4.2.6 Mineral transformation cracks
    4.3 Identification of main types of shale diagenetic fractures
    4.4 Microfracture combinations
5 Shale diagenetic crack diversity and main influencing factors
    5.1 Basic geological characteristics
        5.1.1 Sample diversity
        5.1.2 TOC contents of samples
    5.2 Differences of shale diagenetic fractures
        5.2.1 Shale from marine facies
        5.2.2 Shale from continental facies
        5.2.3 Shale from transitional facies
        5.2.4 Differences in diagenetic fractures of different types of shale
    5.3 Main influencing factors of shale diagenetic fracture formation
        5.3.1 Mineral composition
        5.3.2 Total organic carbon contents
        5.3.3 Maturity of organic matter
        5.3.4 Shale sedimentary facies
6 Conclusions
Gratitude
References
Plate1:SEM photos of microcracks in the shale from marine facies
Plate2:SEM photos of microcracks in the shale from continental facies
Plate3:SEM photos of microcracks in the shale from transitional facies
Appendix



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