0 引言
1 地质背景
2 样品与实验
3 结果与讨论
3.1 页岩有机质丰度与全岩矿物组成特征
表1 下扬子地区望江坳陷二叠系富有机质页岩有机质含量与矿物组成特征Table 1 TOC contents and mineral composition characteristics of Permian organic-rich shale in Wangjiang Depression, Lower Yangtze Region |
层位 | 样品编号 | 深度/m | TOC/% | 矿物组成/% | |||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|
石英 | 钾长石 | 斜长石 | 磷铝矿 | 云母 | 黄铁矿 | 黏土矿物 | 方解石 | 白云石 | |||||
大隆组 | WWD4-11 | 2 278.20 | 10.90 | 33.0 | 2.3 | 0.0 | 4.7 | 9.4 | 0.0 | 31.1 | 17.4 | 2.1 | |
WWD4-13 | 2 280.25 | 6.86 | 45.2 | 2.2 | 0.0 | 14.1 | 0.0 | 0.0 | 33.5 | 5.0 | 0.0 | ||
WWD4-14 | 2 281.30 | 11.60 | 43.6 | 2.1 | 0.0 | 11.8 | 6.0 | 2.3 | 29.8 | 4.4 | 0.0 | ||
WWD4-15 | 2 282.31 | 9.69 | 49.4 | 2.2 | 0.0 | 10.9 | 0.0 | 0.0 | 24.2 | 13.3 | 0.0 | ||
WWD4-17 | 2 284.30 | 4.54 | 48.5 | 3.2 | 0.0 | 11.6 | 0.0 | 0.0 | 25.1 | 11.6 | 0.0 | ||
WWD4-18 | 2 284.90 | 5.21 | 47.1 | 3.6 | 0.0 | 8.0 | 0.0 | 0.0 | 20.3 | 21.0 | 0.0 | ||
吴家坪组 | WWD4-27 | 2 437.20 | 14.50 | 26.6 | 1.7 | 0.0 | 0.0 | 6.6 | 1.9 | 63.2 | 0.0 | 0.0 | |
WWD4-29 | 2 439.10 | 1.24 | 41.0 | 2.0 | 0.0 | 13.1 | 6.0 | 2.2 | 35.7 | 0.0 | 0.0 | ||
WWD4-31 | 2 441.20 | 1.23 | 34.2 | 4.4 | 0.0 | 4.8 | 22.0 | 0.0 | 34.6 | 0.0 | 0.0 | ||
WWD4-33 | 2 443.20 | 1.16 | 42.8 | 2.4 | 0.0 | 5.6 | 9.8 | 0.0 | 39.4 | 0.0 | 0.0 | ||
WWD4-35 | 2 445.30 | 1.37 | 50.1 | 2.5 | 0.0 | 7.4 | 7.7 | 0.0 | 32.3 | 0.0 | 0.0 | ||
WWD4-37 | 2 447.10 | 0.29 | 50.7 | 2.3 | 0.0 | 9.2 | 0.0 | 0.0 | 37.8 | 0.0 | 0.0 |
3.2 孔隙类型及微观特征
图2 大隆组与吴家坪组页岩孔隙类型及微观特征FE-SEM照片(a)WWD4-11,2 278.2 m,草莓状黄铁矿中发育较多粒间孔,周边见少量黏土矿物晶间孔和碎屑矿物粒间孔;(b)WWD4-11,2 278.2 m,长条状纳米级别脆性矿物成岩收缩缝,另可见少量黏土矿物晶间和粒间微孔;(c)WWD4-11,2 278.2 m,脆性矿物粒间纳米级别孔缝;(d)WWD4-17,2 284.3 m,圆形溶蚀粒内孔后期充填丝缕状伊利石;(e)WWD4-17,2 284.3 m,丝缕状伊利石内发育片状、狭缝状等不规则晶间孔;(f)WWD4-27,2 437.2 m,狭缝状、长条状原生残余粒间孔缝;(g)WWD4-27,2 437.2 m,草莓状黄铁矿整体与周围介质间发育矿物收缩缝,周围有机质中不发育有机质孔;(h)WWD4-27,2 437.2 m,矿物颗粒边缘及周围伊利石和伊/蒙混层中分别发育收缩缝和黏土矿物粒间孔;(i)WWD4-35,2 445.3 m,分散狭缝、不规则形状粒间孔及黏土矿物粒间孔,偶见有机质发育 Fig.2 FE-SEM images of pore types and microscopic characteristics of shale in Dalong and Wujiaping formations |
3.3 孔隙结构特征
表2 下扬子地区望江坳陷大隆组和吴家坪组页岩比表面积与孔容特征Table 2 Characteristics of specific surface area and pore volume of shale in Dalong Formation and Wujiaping Formation in Wangjiang Depression of Lower Yangtze Region |
层位 | 样品编号 | 深度/m | 氮气吸附 | 二氧化碳吸附 | ||||
---|---|---|---|---|---|---|---|---|
BET比表面积/(m2/g) | 孔容/(mL/g) | 平均孔直径/nm | DR比表面积/(m2/g) | 微孔孔容/(mL/g) | 平均孔直径/nm | |||
大隆组 | WWD4-11 | 2 278.20 | 5.858 | 0.009 7 | 7.761 | 23.012 | 0.009 | 0.848 |
WWD4-13 | 2 280.25 | 8.838 | 0.008 0 | 4.965 | 18.82 | 0.007 | 0.865 | |
WWD4-14 | 2 281.30 | 20.062 | 0.017 6 | 5.002 | 24.077 | 0.009 | 0.855 | |
WWD4-15 | 2 282.31 | 12.945 | 0.014 4 | 5.825 | 20.7 | 0.008 | 0.823 | |
WWD4-17 | 2 284.30 | 4.335 | 0.003 5 | 4.696 | 7.03 | 0.003 | 0.853 | |
WWD4-18 | 2 284.90 | 7.671 | 0.008 8 | 5.884 | 16.798 | 0.006 | 0.854 | |
吴家坪组 | WWD4-27 | 2 437.20 | 12.352 | 0.010 4 | 4.868 | 41.044 | 0.015 | 0.819 |
WWD4-29 | 2 439.10 | 2.783 | 0.004 5 | 7.502 | 11.79 | 0.004 | 0.784 | |
WWD4-31 | 2 441.20 | 3.975 | 0.009 0 | 10.02 | 12.114 | 0.005 | 0.784 | |
WWD4-33 | 2 443.20 | 8.588 | 0.009 6 | 5.884 | 11.873 | 0.004 | 0.825 | |
WWD4-35 | 2 445.30 | 7.567 | 0.009 5 | 6.414 | 11.887 | 0.004 | 0.864 | |
WWD4-37 | 2 447.10 | 7.607 | 0.008 2 | 5.789 | 10.086 | 0.004 | 0.869 |
表3 页岩微孔、介孔和大孔的比表面积和孔隙容积Table 3 Specific surface area and pore volume of shale micropores, mesopores and macropores |
样品编号 | 比表面积/(m2/g) | 孔隙容积/(cm3/g) | ||||||
---|---|---|---|---|---|---|---|---|
总和 | 微孔 | 介孔 | 大孔 | 总和 | 微孔 | 介孔 | 大孔 | |
WWD4-11 | 29.264 7 | 24.010 0 | 5.175 8 | 0.078 9 | 0.017 0 | 0.007 4 | 0.008 1 | 0.0015 |
WWD4-13 | 24.303 1 | 19.431 8 | 4.832 9 | 0.038 4 | 0.013 1 | 0.006 0 | 0.006 3 | 0.000 7 |
WWD4-14 | 36.959 7 | 25.709 1 | 11.092 6 | 0.158 0 | 0.026 5 | 0.008 1 | 0.015 4 | 0.003 0 |
WWD4-15 | 30.314 1 | 22.719 4 | 7.458 0 | 0.136 7 | 0.020 8 | 0.006 9 | 0.011 3 | 0.002 6 |
WWD4-17 | 9.576 6 | 7.579 5 | 1.972 5 | 0.024 6 | 0.005 6 | 0.002 4 | 0.002 7 | 0.000 5 |
WWD4-18 | 22.188 7 | 17.651 3 | 4.470 4 | 0.067 0 | 0.013 4 | 0.005 5 | 0.006 6 | 0.001 3 |
WWD4-27 | 53.108 0 | 30.515 0 | 8.399 3 | 0.076 0 | 0.025 6 | 0.013 4 | 0.010 8 | 0.001 4 |
WWD4-29 | 16.827 3 | 13.945 1 | 2.879 8 | 0.002 4 | 0.009 4 | 0.004 3 | 0.005 0 | 0.000 1 |
WWD4-31 | 18.202 8 | 14.302 0 | 3.772 7 | 0.128 1 | 0.014 0 | 0.004 4 | 0.007 1 | 0.002 5 |
WWD4-33 | 19.746 4 | 13.467 0 | 6.186 9 | 0.092 5 | 0.015 0 | 0.004 2 | 0.009 2 | 0.001 6 |
WWD4-35 | 18.641 9 | 12.693 6 | 5.836 5 | 0.111 8 | 0.014 7 | 0.004 1 | 0.008 9 | 0.001 8 |
WWD4-37 | 16.499 0 | 10.930 3 | 5.475 7 | 0.093 0 | 0.012 9 | 0.003 6 | 0.007 5 | 0.001 7 |
3.4 分型维数模型与计算
表4 页岩样品FHH分形维数计算Table 4 Calculation of FHH fractal dimension of shale samples |
样品编号 | P/P 0=0~0.5 | P/P 0=0.5~1 | ||||
---|---|---|---|---|---|---|
λ 1 | R 2 | D 1=3+λ 1 | λ 2 | R 2 | D 2=3+λ 2 | |
WWD4-11 | -0.652 9 | 0.978 0 | 2.347 1 | -0.222 2 | 0.948 4 | 2.777 8 |
WWD4-13 | -0.591 4 | 0.962 2 | 2.408 6 | -0.140 4 | 0.922 8 | 2.859 6 |
WWD4-14 | -0.489 9 | 0.955 8 | 2.510 1 | -0.152 7 | 0.956 5 | 2.847 3 |
WWD4-15 | -0.563 7 | 0.953 2 | 2.436 3 | -0.181 5 | 0.969 1 | 2.818 5 |
WWD4-17 | -0.550 9 | 0.918 1 | 2.449 1 | -0.130 7 | 0.938 1 | 2.869 3 |
WWD4-18 | -0.580 2 | 0.957 8 | 2.419 8 | -0.166 5 | 0.944 0 | 2.833 5 |
WWD4-27 | -0.415 4 | 0.993 8 | 2.584 6 | -0.144 7 | 0.924 6 | 2.855 3 |
WWD4-29 | -0.668 0 | 0.984 1 | 2.332 0 | -0.224 6 | 0.919 0 | 2.775 4 |
WWD4-31 | -0.670 2 | 0.974 0 | 2.329 8 | -0.298 9 | 0.966 6 | 2.701 1 |
WWD4-33 | -0.430 5 | 0.982 5 | 2.569 5 | -0.174 5 | 0.960 0 | 2.825 5 |
WWD4-35 | -0.443 0 | 0.988 3 | 2.557 0 | -0.200 8 | 0.947 8 | 2.799 2 |
WWD4-37 | -0.445 7 | 0.977 7 | 2.554 3 | -0.172 1 | 0.937 1 | 2.827 9 |
3.5 页岩孔隙的主控因素研究
3.5.1 页岩孔隙特征参数与有机质丰度的关系
3.5.2 页岩孔隙特征参数与黏土矿物含量的关系
图8 下扬子地区望江坳陷二叠系大隆组和吴家坪组页岩比表面积与孔体积与黏土矿物含量之间的关系Fig.8 Relationship between specific surface area, pore volume and clay mineral content of shale in the Permian Dalong Formation and Wujiaping Formation in the Wangjiang Depression of the Lower Yangtze Region |