Micropore inhomogeneity of continental shale under different side length and resolution: a case study of Chang 72 shale from well Yaoke 1 in Ordos Basin
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摘要: 陆相页岩的非均质性与海相页岩不同,其主要表现为孔隙结构的非均质性。以鄂尔多斯盆地瑶科1井采出的上三叠统长72黑色页岩为例,利用微米CT在1 μm分辨率下对7个不同边长(100~700 μm)、纳米CT在65 nm分辨率下对4个不同边长(10~39 μm)的孔隙和裂缝进行了观测和分析。建立了3D图像重构基础上的不同边长及分辨率的孔隙指标非均质特性表征:孔隙数量和体积随边长增加而呈指数增大,面密度随边长增大而减小,长宽平均值及其比值基本不变。作为表征连通性指标的配位数与孔隙长度均值关系较为密切。Abstract: Continental shale is different from marine shale due to its inhomogeneity, which is apparent mainly in the inhomogeneity of pore structure. The Upper Triassic Yanchang black shale (Chang 72) samples were collected from the well Yaoke 1 in the Ordos Basin. Micro and nano CT were used to observe and analyze the pores and cracks of 7 different side lengths (100-700 μm) and 4 different side lengths (10-39 μm) at 1 μm and 65 nm resolutions, respectively. The spatial inhomogeneity index of different side lengths and resolutions based on 3D image reconstruction was established. It was found that the number and volume of pores increased exponentially with the increase of side lengths, while the plane density of the pores decreased with the increase of side lengths. The average length, width and their ratio remained basically unchanged. Coordination number, as an indicator of connectivity, is closely related to the average width of pores.
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Key words:
- micropore /
- block side length /
- plane density of pores /
- ratio of pore length with width /
- Yanchang shale /
- Ordos Basin
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表 1 微米—纳米CT扫描实验条件
Table 1. Micro CT and Nano CT scanning situations
检测类型 仪器型号 视域 像素 分辨率 样品规格 3D方块边长/μm 二维灰度图像 微米CT Xradia micro CT VERSA-500 2 mm×2 mm 2 048×2 048 1 μm 圆柱, Φ2 mm, 高2 mm 100, 200, 300, 400, 500, 600, 700 1 984张 纳米CT Xradia L-200 Nano CT ULTRAXRM 65 μm×65 μm 1 024×1 024 65 nm 圆柱, Φ65 μm, 高65μm 10, 20, 30, 39 1 021张 表 2 不同边长立方块的孔隙特征
Table 2. Pore features of cubic blocks at 11 different side lengths
边长/μm 孔隙数/个 裂隙数/个 (孔隙+裂隙)数/个 (孔隙+裂隙)体积/μm3 总体积/μm3 孔隙度/% (孔隙+裂隙)总长/μm 面密度/(μm·μm-2) 长/μm 宽/μm 长/宽 喉道与孔隙半径比 配位数 10 210 150 360 20.35 906.28 2.245 142.281 1.423 $\frac{{0.092 \sim 10.022}}{{0.395}}$ $\frac{{0.065 \sim 3.775}}{{0.214}}$ $\frac{{0.96 \sim 4.00}}{{1.86}}$ $\frac{{0 \sim 9}}{{1.66}}$ 20 1 268 854 2 122 111.88 7 301.73 1.532 895.622 2.239 $\frac{{0.092 \sim 11.866}}{{0.422}}$ $\frac{{0.065 \sim 5.196}}{{0.230}}$ $\frac{{0.96 \sim 6.00}}{{1.83}}$ $\frac{{1 \sim 10}}{{1.71}}$ 30 3 894 550 4 444 406.00 2.63×104 1.542 1 779.817 1.978 $\frac{{0.092 \sim 14.149}}{{0.401}}$ $\frac{{0.065 \sim 9.463}}{{0.221}}$ $\frac{{0.96 \sim 5.40}}{{1.83}}$ $\frac{{0 \sim 9}}{{1.64}}$ 39 2 307 1578 3 885 539.06 5.88×104 0.917 1 654.060 1.087 $\frac{{0.092 \sim 15.255}}{{0.426}}$ $\frac{{0.065 \sim 8.227}}{{0.223}}$ $\frac{{1.00 \sim 10.00}}{{1.93}}$ $\frac{{0.04 \sim 0.96}}{{0.33}}$ $\frac{{1 \sim 12}}{{1.68}}$ 100 253 190 443 3.49×104 9.64×105 3.620 3 204.079 0.320 $\frac{{1.414 \sim 72.717}}{{7.233}}$ $\frac{{1.000 \sim 21.920}}{{3.383}}$ $\frac{{1.00 \sim 9.00}}{{2.00}}$ $\frac{{0.29 \sim 1.09}}{{0.63}}$ $\frac{{0 \sim 4}}{{1.44}}$ 200 1 632 735 2 367 2.51×105 7.74×106 3.248 1.877×104 0.469 $\frac{{1.414 \sim 66.468}}{{7.929}}$ $\frac{{1.000 \sim 26.839}}{{3.757}}$ $\frac{{1.00 \sim 8.01}}{{2.04}}$ $\frac{{0.17 \sim 1.30}}{{0.52}}$ $\frac{{0 \sim 6}}{{1.58}}$ 300 4 444 1 458 5 902 1.06×106 2.59×107 4.073 3.330×104 0.370 $\frac{{1.414 \sim 89.239}}{{7.493}}$ $\frac{{1.000 \sim 41.754}}{{3.662}}$ $\frac{{0.96 \sim 9.19}}{{1.95}}$ 400 4 785 6 464 1.12×104 2.39×106 6.16×107 3.882 3.927×104 0.245 $\frac{{1.414 \sim 106.000}}{{8.836}}$ $\frac{{1.000 \sim 36.338}}{{4.038}}$ $\frac{{1.00 \sim 10.00}}{{2.11}}$ $\frac{{0.09 \sim 2.18}}{{0.48}}$ $\frac{{0 \sim 11}}{{1.86}}$ 500 4 444 1.67×104 2.11×104 4.29×106 1.21×108 3.554 4.038×104 0.162 $\frac{{1.414 \sim 94.173}}{{9.087}}$ $\frac{{1.000 \sim 39.294}}{{4.126}}$ $\frac{{0.96 \sim 12.00}}{{2.11}}$ 600 1.71×104 2.07×104 3.78×104 8.22×106 2.08×108 3.959 4.044×104 0.112 $\frac{{1.414 \sim 84.247}}{{9.100}}$ $\frac{{1.000 \sim 30.249}}{{4.054}}$ $\frac{{0.92 \sim 9.00}}{{2.16}}$ $\frac{{0.09 \sim 2.18}}{{0.49}}$ $\frac{{0 \sim 12}}{{1.81}}$ 700 4.44×104 1.96×104 6.41×104 1.43×107 3.28×108 4.364 4.118×104 0.084 $\frac{{1.414 \sim 106.177}}{{9.266}}$ $\frac{{1.000 \sim 40.213}}{{4.163}}$ $\frac{{0.96 \sim 9.42}}{{2.13}}$ 注:表中分式的意义为:$\frac{{最小值 \sim 最大值}}{{平均值}}$。 -
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