Mechanical Properties of Lamellar Shale Considering the Effect of Rock Structure and Hydration from Macroscopic and Microscopic Points of View
It is well known that the effect of shale hydration causes wellbore instability due to water phase invasion of drilling fluid to lamellar shale rich formations. This is because of that the mechanical properties (compressive strength, elastic modulus, etc.) of lamellar shale surrounding the borehole,...
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| Format: | Article |
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MDPI AG
2022-01-01
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| Series: | Applied Sciences |
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| Online Access: | https://www.mdpi.com/2076-3417/12/3/1026 |
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| author | Qiangui Zhang Lizhi Wang Pengfei Zhao Xiangyu Fan Feitao Zeng Bowei Yao Liang He Simin Yang Yang Feng |
| author_facet | Qiangui Zhang Lizhi Wang Pengfei Zhao Xiangyu Fan Feitao Zeng Bowei Yao Liang He Simin Yang Yang Feng |
| author_sort | Qiangui Zhang |
| collection | DOAJ |
| description | It is well known that the effect of shale hydration causes wellbore instability due to water phase invasion of drilling fluid to lamellar shale rich formations. This is because of that the mechanical properties (compressive strength, elastic modulus, etc.) of lamellar shale surrounding the borehole, which is rich in clay minerals, will decrease significantly after hydration. In this study, using the lamellar shale in the continental stratum of the southern Ordos Basin, the mechanical properties of lamellar shale were studied by compression tests considering the effect of lamellar structure and hydration from a macroscopic point of view. In addition, the mechanical mechanism was discussed combined with the CT scanning tests results from a microscopic point of view. The results demonstrate the following points. Lamellar shale has stronger anisotropy than bedding shale, the compressive strength (deviatoric stress) and elastic modulus of lamellar shale are both lower than those of bedding shale, and it is more prone to tension fracture. With the increase in the angle (<i>β</i>) between the lamina and the axial direction from 0° to 90°, the compressive strength of lamellar shale decreases when <i>β</i> < 30° and then increases, the elastic modulus of lamellar shale decreases greatly when <i>β</i> < 30° and then tends to flatten. With the increase in hydration time, the compressive strength and elastic modulus of lamellar shale both gradually decrease, and the rates of their decrements reduce. The mechanical properties of lamellar shale are more affected by hydration than those of bedding shale. The hydration of lamellar shale leads to the formation of new fractures and the expansion of existing fractures in the junction area between the laminae and rock matrix, resulting in easy tension fracture along the laminae of shale. |
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| issn | 2076-3417 |
| language | English |
| last_indexed | 2024-03-10T00:16:10Z |
| publishDate | 2022-01-01 |
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| series | Applied Sciences |
| spelling | doaj.art-a2e5509243e44217bd88cb400446516d2023-11-23T15:50:38ZengMDPI AGApplied Sciences2076-34172022-01-01123102610.3390/app12031026Mechanical Properties of Lamellar Shale Considering the Effect of Rock Structure and Hydration from Macroscopic and Microscopic Points of ViewQiangui Zhang0Lizhi Wang1Pengfei Zhao2Xiangyu Fan3Feitao Zeng4Bowei Yao5Liang He6Simin Yang7Yang Feng8Petroleum Engineering School, Southwest Petroleum University, Chengdu 610500, ChinaPetroleum Engineering School, Southwest Petroleum University, Chengdu 610500, ChinaSchool of Geoscience and Technology, Southwest Petroleum University, Chengdu 610500, ChinaSchool of Geoscience and Technology, Southwest Petroleum University, Chengdu 610500, ChinaDepartment of Civil, Geological and Mining Engineering, École Polytechnique de Montréal, Montreal, QC H3T 1J4, CanadaPetroleum Engineering School, Southwest Petroleum University, Chengdu 610500, ChinaSchool of Geoscience and Technology, Southwest Petroleum University, Chengdu 610500, ChinaPetroleum Engineering School, Southwest Petroleum University, Chengdu 610500, ChinaSchool of Geoscience and Technology, Southwest Petroleum University, Chengdu 610500, ChinaIt is well known that the effect of shale hydration causes wellbore instability due to water phase invasion of drilling fluid to lamellar shale rich formations. This is because of that the mechanical properties (compressive strength, elastic modulus, etc.) of lamellar shale surrounding the borehole, which is rich in clay minerals, will decrease significantly after hydration. In this study, using the lamellar shale in the continental stratum of the southern Ordos Basin, the mechanical properties of lamellar shale were studied by compression tests considering the effect of lamellar structure and hydration from a macroscopic point of view. In addition, the mechanical mechanism was discussed combined with the CT scanning tests results from a microscopic point of view. The results demonstrate the following points. Lamellar shale has stronger anisotropy than bedding shale, the compressive strength (deviatoric stress) and elastic modulus of lamellar shale are both lower than those of bedding shale, and it is more prone to tension fracture. With the increase in the angle (<i>β</i>) between the lamina and the axial direction from 0° to 90°, the compressive strength of lamellar shale decreases when <i>β</i> < 30° and then increases, the elastic modulus of lamellar shale decreases greatly when <i>β</i> < 30° and then tends to flatten. With the increase in hydration time, the compressive strength and elastic modulus of lamellar shale both gradually decrease, and the rates of their decrements reduce. The mechanical properties of lamellar shale are more affected by hydration than those of bedding shale. The hydration of lamellar shale leads to the formation of new fractures and the expansion of existing fractures in the junction area between the laminae and rock matrix, resulting in easy tension fracture along the laminae of shale.https://www.mdpi.com/2076-3417/12/3/1026lamellar shalemechanical propertiesanisotropyhydrationfailure characteristics |
| spellingShingle | Qiangui Zhang Lizhi Wang Pengfei Zhao Xiangyu Fan Feitao Zeng Bowei Yao Liang He Simin Yang Yang Feng Mechanical Properties of Lamellar Shale Considering the Effect of Rock Structure and Hydration from Macroscopic and Microscopic Points of View Applied Sciences lamellar shale mechanical properties anisotropy hydration failure characteristics |
| title | Mechanical Properties of Lamellar Shale Considering the Effect of Rock Structure and Hydration from Macroscopic and Microscopic Points of View |
| title_full | Mechanical Properties of Lamellar Shale Considering the Effect of Rock Structure and Hydration from Macroscopic and Microscopic Points of View |
| title_fullStr | Mechanical Properties of Lamellar Shale Considering the Effect of Rock Structure and Hydration from Macroscopic and Microscopic Points of View |
| title_full_unstemmed | Mechanical Properties of Lamellar Shale Considering the Effect of Rock Structure and Hydration from Macroscopic and Microscopic Points of View |
| title_short | Mechanical Properties of Lamellar Shale Considering the Effect of Rock Structure and Hydration from Macroscopic and Microscopic Points of View |
| title_sort | mechanical properties of lamellar shale considering the effect of rock structure and hydration from macroscopic and microscopic points of view |
| topic | lamellar shale mechanical properties anisotropy hydration failure characteristics |
| url | https://www.mdpi.com/2076-3417/12/3/1026 |
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