Influence factors and conduction mechanism of mature lacustrine shales: a case study of the first member of Qingshankou Formation in Changling Sag, South Songliao Basin
Received date: 2023-12-25
Online published: 2024-12-19
Copyright
High clay content, a variety of pore forms, and complicated fluid occurrence are characteristics of shale reservoirs. Shale's electrical conductivity is influenced by many factors, including its mineral composition, fluid type, physical properties and maturity, which leads to the weak correlation between electrical conductivity and oil content and physical properties. Therefore, it is critical to understand the conductive mechanism and influence factors of the electrical properties of shale. In this paper, the mature lacustrine shale of the first member of the Qingshankou Formation (Qing1 Member) in Changling Sag, south Songliao Basin is taken as an example. Using sealed coring, Two-dimensional nuclear magnetic resonance, field emission scanning electron microscopy, TOC, and X-ray Diffraction tests, combined with electrical logging curves, the impacts of fluid occurrence, physical properties and mineral composition on the electrical properties of the shale were analyzed, and then the conduction mechanism of mature lacustrine shale was addressed. The findings indicate that physical properties have a minor impact on shale electrical properties, while mineral composition (carbonates minerals, clay minerals) and fluid type have a significant impact. Silty-laminated shales (including shell limestone) are affected electrically by carbonate minerals, clay minerals, oil saturation, free water and bound water, argillaceous-laminated felsic shales and argillaceous-laminated clay shales are affected electrically by bound water, adsorbed oil, and clay minerals. For mature lacustrine shale, there are three different types of conductivity mechanisms: clay additional conduction (type Ⅰ), organic matter and clay complex conduction (type Ⅱ), and porous conduction of brittle mineral matrix (type Ⅲ). Silty-laminated shales mainly develop conductivity mechanisms of porous conduction of brittle mineral matrix and clay additional conduction, whereas argillaceous-laminated felsic shales and argillaceous-laminated clay shale primarily develop conductivity mechanisms of clay additional conduction and clay additional conduction. The findings provide guidance for enriching the electrical conductivity mechanism of shale and raising the accuracy of shale saturation interpretation.
Wei DANG , DianShi XIAO , ShiWen Han , Liang YANG , Zhuo LI , LeHua ZHENG , Rui WANG . Influence factors and conduction mechanism of mature lacustrine shales: a case study of the first member of Qingshankou Formation in Changling Sag, South Songliao Basin[J]. Progress in Geophysics, 2024 , 39(5) : 1935 -1950 . DOI: 10.6038/pg2024HH0464
图3 松辽盆地长岭和古龙凹陷青一段页岩二维核磁共振流体识别图版对比(a)长岭凹陷青一段页岩储层二维核磁共振流体识别图版;(b)古龙凹陷青山口组页岩二维核磁共振流体识别图版(据白龙辉等,2021;石玉江等,2023修改). Fig 3 Comparisons of 2D-NMR fluid identification pattern of Qing1 Member shale in Changling and Gulong Sag of Songliao Basin (a)2D-NMR fluid identification pattern of Qing1 Member shale in Changling Sag; (b)2D-NMR fluid identification pattern of Qingshankou Formation shale in Gulong Sag(Modified by Bai et al., 2021; Shi et al., 2023). |
图4 长岭凹陷A井青一段页岩岩相薄片特征(a)粉砂纹层页岩(深度:2392.38 m);(b)介壳灰岩(深度:2370.18 m);(c)泥纹层长英质页岩(深度:2383.90 m);(d)泥纹层黏土质页岩(深度:2398.90 m). Fig 4 Thin section characteristics of lithofacies of Qing1 Member shale in well A of the Changling Sag (a)Silty-laminated shales(depth: 2392.38 m); (b)Shell limestone(depth: 2370.18 m); (c)Argillaceous-laminated felsic shales (depth: 2383.90 m); (d)Argillaceous-laminated clay shales(depth: 2398.90 m). |
图5 长岭凹陷A井青一段页岩主要孔隙类型镜下特征(a)粒间孔,粉砂纹层页岩(深度:2369.96 m);(b)粒间溶蚀孔,粉砂纹层页岩(深度:2382.25 m);(c)粒内溶蚀孔,泥纹层长英质页岩(深度:2378.90 m);(d)黏土晶间孔,泥纹层长英质页岩(深度:2378.90 m);(e)黄铁矿晶间孔,泥纹层长英质页岩(深度:2382.25 m);(f)黏土晶间孔被有机质填充,泥纹层黏土质页岩(深度:2404.16 m);(g)有机质孔,粉砂纹层页岩(深度:2369.96 m);(h)微裂缝,含介壳粉砂纹层页岩(深度:2409.50 m);(i)有机质与黏土复合体,泥纹层黏土质页岩(深度:2404.16 m). Fig 5 Microscopic characteristics of main pore types of Qing1 Member shale in well A of Changling Sag (a)Intergranular pore, silty-laminated shales(depth: 2369.96 m); (b)Intergranular dissolution pore, silty-laminated shales(depth: 2382.25 m); (c)Intragranular dissolution pore, argillaceous-laminated felsic shales(depth: 2378.90 m); (d)Clay intercrystalline pore, argillaceous-laminated felsic shales(depth: 2378.90 m); (e)Pyrite intercrystalline pore, argillaceous-laminated felsic shales(depth: 2382.25 m); (f)Clay intergranular pores are filled with organic matter, argillaceous-laminated clay shales(depth: 2404.16 m); (g)Organic pore, silty-laminated shales(depth: 2369.96 m); (h)Microfracture, Silt-laminated shale with shell(depth: 2409.50 m); (i)Organic matter and clay complex, argillaceous-laminated clay shales(depth: 2404.16 m). |
表1 长岭凹陷A井青一段页岩物性及含油性特征分布Table 1 Physical properties and oil bearing characteristics distribution of Qing1 Member shale in well A of Changling Sag |
| 物性及含油性参数 | 总体 | 介壳灰岩 | 粉砂纹层页岩 | 泥纹层长英质页岩 | 泥纹层黏土质页岩 | |
| 有效孔隙度/% | 分布范围 | 1.19~10.23 | 1.19~8.49 | 4.15~7.16 | 4.05~9.76 | 5.26~10.23 |
| 均值 | 7.09 | 5.51 | 5.83 | 7.47 | 7.56 | |
| 含油饱和度/% | 分布范围 | 30.79~75.90 | 31.10~67.55 | 35.72~55.36 | 37.53~75.90 | 30.79~71.79 |
| 均值 | 48.71 | 48.60 | 48.10 | 50.10 | 47.42 | |
| 游离油含量/(mg/g) | 分布范围 | 1.62~13.08 | 1.62~11.78 | 4.57~10.17 | 6.03~13.08 | 4.94~9.26 |
| 均值 | 7.81 | 6.64 | 6.90 | 9.36 | 6.79 | |
| 吸附油含量/(mg/g) | 分布范围 | 1.05~10.49 | 1.05~3.13 | 2.67~4.88 | 1.93~9.25 | 2.20~10.49 |
| 均值 | 4.51 | 2.01 | 3.76 | 4.36 | 5.69 | |
| 游离油占比/% | 分布范围 | 38.29~86.88 | 57.57~86.88 | 56.89~70.54 | 39.55~86.17 | 38.29~79.75 |
| 均值 | 63.61 | 71.56 | 64.52 | 68.37 | 55.75 | |
| 游离水含量/(mg/g) | 分布范围 | 2.11~30.47 | 2.11~26.07 | 9.54~17.49 | 6.53~28.97 | 9.04~30.47 |
| 均值 | 17.21 | 14.19 | 14.30 | 18.29 | 17.88 | |
| 结合水含量/(mg/g) | 分布范围 | 4.32~66.14 | 4.32~51.38 | 22.75~42.60 | 27.09~66.14 | 46.94~63.91 |
| 均值 | 46.70 | 22.72 | 31.24 | 48.00 | 57.45 | |
| 游离水占比/% | 分布范围 | 8.99~54.32 | 28.46~54.32 | 23.96~37.91 | 8.99~40.75 | 12.62~34.79 |
| 均值 | 27.98 | 40.88 | 31.67 | 27.46 | 23.43 | |
图6 长岭凹陷A井青一段页岩岩心深度归位(a)成像测井图(A井,2403.00~2406.00 m);(b,c)取心介壳灰岩岩心照片(A井,深度段分别为2405.52~2405.57 m、2405.99~2406.05 m). Figure 6 Shale core-depth homing process of Qing1 Member shale in well A of Changling Sag (a)Imaging logging(well A, 2403.00~2406.00 m); (b, c)Core photograph of shell limestone(well A, The depth segments are 2405.52~2405.57 m、2405.99~2406.05 m). |
感谢审稿专家提出的修改意见和编辑部的大力支持!
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