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煤层水力压裂应力与裂隙演化的细观规律

李全贵 邓羿泽 胡千庭 张跃兵 宋明洋 刘继川 石佳林

李全贵,邓羿泽,胡千庭,等. 煤层水力压裂应力与裂隙演化的细观规律[J]. 煤田地质与勘探,2022,50(6):32−40 doi: 10.12363/issn.1001-1986.21.10.0603
引用本文: 李全贵,邓羿泽,胡千庭,等. 煤层水力压裂应力与裂隙演化的细观规律[J]. 煤田地质与勘探,2022,50(6):32−40 doi: 10.12363/issn.1001-1986.21.10.0603
LI Quangui,DENG Yize,HU Qianting,et al. Mesoscopic law of stress and fracture evolution of coal seams hydraulic fracturing[J]. Coal Geology & Exploration,2022,50(6):32−40 doi: 10.12363/issn.1001-1986.21.10.0603
Citation: LI Quangui,DENG Yize,HU Qianting,et al. Mesoscopic law of stress and fracture evolution of coal seams hydraulic fracturing[J]. Coal Geology & Exploration,2022,50(6):32−40 doi: 10.12363/issn.1001-1986.21.10.0603

煤层水力压裂应力与裂隙演化的细观规律

doi: 10.12363/issn.1001-1986.21.10.0603
基金项目: 国家自然科学基金项目(52074049)
详细信息
    第一作者:

    李全贵,1986年生,男,河南民权人,博士,副教授,从事煤矿瓦斯防治、煤层气开发. E-mail:liqg@cqu.edu.cn

  • 中图分类号: TD163;TE377

Mesoscopic law of stress and fracture evolution of coal seams hydraulic fracturing

  • 摘要: 水力压裂作为煤层强化增透技术的一种,其应力演化特征及裂隙形态与扩展范围的判断尤为重要。采用离散元数值方法,以导向压裂为背景,建立水力压裂流固耦合模型;通过应力路径、裂纹热点图等手段,探究水力压裂过程中压裂排量、泊松比、天然裂隙密度对应力演化和裂隙演化的影响及其细观规律。结果表明:不同压裂排量下的应力演化方向及最终应力路径曲线形状有着明显的不同,低排量下裂隙附近的应力比值逐渐增大,而在高排量下先增大后减小;煤层泊松比越大,平均压裂半径越低,但对起裂时间及裂隙的扩展形态影响不明显;天然裂隙的发育情况对水力裂隙的扩展起着关键性作用,高裂隙发育煤层水力裂隙扩展的方向性无法预测,应力演化方向会出现反转现象;压裂过程中不同区域的应力演化特征能够反映出裂隙的扩展状态,现场可通过监测压裂区域附近应力变化,判断水力压裂缝网的扩展范围。

     

  • 图  单轴压缩标定结果

    Fig. 1  Calibration results of uniaxial compression

    图  巴西劈裂标定结果

    Fig. 2  Calibration results of Brazilian split

    图  管域模型

    Fig. 3  Pipe-domain model

    图  水力压裂模型

    Fig. 4  Hydraulic fracturing model

    图  微裂隙扩展形态

    Fig. 5  Schematic diagram of microcrack propagation

    图  不同排量下水力压裂应力与裂隙细观演化特征

    Fig. 6  Mesoscopic evolution of hydraulic fracturing stress and fracture at different flow rates

    图  不同泊松比下水力压裂应力与裂隙细观演化特征

    Fig. 7  Mesoscopic evolution of hydraulic fracturing stress and fracture under different Poisson’s ratios

    图  不同天然裂隙密度下水力压裂应力与裂隙细观演化特征

    Fig. 8  Mesoscopic evolution of hydraulic fracturing stress and fracture under different natural fracture density

    表  1  试样宏观参数与模型宏观参数的比较

    Table  1  Comparison between sample macro parameters and model macro parameters

    宏观力学参数实际值PFC2D
    计算值
    误差/%
    单轴抗压强度σc/MPa 32.22 32.04 −0.5
    弹性模量E/GPa 1.81 1.82 0.5
    泊松比ν 0.25
    本体抗拉强度σt/MPa 2.83 2.96 4.6
    下载: 导出CSV

    表  2  模型细观参数

    Table  2  Model mesoscopic parameters

    参数类别细观参数数值
    颗粒 颗粒最小半径Rmin/mm 0.30
    最大最小粒径比Rmax/Rmin 1.66
    颗粒密度ρ/(kg∙m−3) 1 280
    孔隙率/% 9
    阻尼β/(Ns∙m−1) 0.50
    接触模型 细观弹性模量Ec/GPa 1.00
    刚度比kn/ks 2.30
    摩擦因数μ 0.50
    细观抗拉强度σc/MPa 11
    黏聚力c/MPa 20
    摩擦角φ/(°) 37.50
    法向临界阻尼比βn 0.57
    下载: 导出CSV

    表  3  水力压裂模拟方案设计

    Table  3  Scheme design of hydraulic fracturing simulation

    序号天然裂隙
    密度
    煤体泊松比压裂排量Q/(mL∙min−1)
    10.2520
    20.2540
    30.2560
    40.1640
    50.3540
    60.2540
    70.2540
    80.2540
    注:低、中、高泊松比分别代表ν = 0.16、ν = 0.25、ν = 0.35;低、中、高压裂排量分别代表Q = 20、Q = 40、Q = 60 mL/min;低、中、高天然裂隙密度分别代表与参考线相交的裂隙数量为5、10、20个。
    下载: 导出CSV
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  • 收稿日期:  2021-11-01
  • 修回日期:  2022-01-13
  • 发布日期:  2022-06-25
  • 网络出版日期:  2022-05-30

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