Clarifying the contribution of multiscale pores to physical properties of Chang 7 tight sandstones: insight from full-scale pore structure and fractal characteristics
The pore structure and its heterogeneity of tight reservoirs are key factors affecting the storage and percolation of crude oil. The pore system of Chang 7 tight sandstone has multi-scale and multi-type characteristics. However, the contribution of different pore types and pore sizes to the physical...
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Frontiers Media S.A.
2024-02-01
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| Series: | Frontiers in Earth Science |
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| Online Access: | https://www.frontiersin.org/articles/10.3389/feart.2024.1361052/full |
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| author | Zhen Li Zhen Li Yilin Ren Rui Chang Yuanli Zhang Xuze Zhang Weichao Tian |
| author_facet | Zhen Li Zhen Li Yilin Ren Rui Chang Yuanli Zhang Xuze Zhang Weichao Tian |
| author_sort | Zhen Li |
| collection | DOAJ |
| description | The pore structure and its heterogeneity of tight reservoirs are key factors affecting the storage and percolation of crude oil. The pore system of Chang 7 tight sandstone has multi-scale and multi-type characteristics. However, the contribution of different pore types and pore sizes to the physical properties of Chang 7 tight sandstone is still unclear. In this paper, we collected a suite of Chang 7 tight sandstones to investigate the full-scale pore structure and fractal characteristics by casting thin section, field emission scanning electron microscope, two-dimensional multi-scale backscattered scanning electron microscopy, N2 adsorption (NA) and NMR. The pore diameters of Chang 7 tight sandstone are usually distributed between 0.001 and 20 μm. Intercrystalline pores are mainly distuibuted <500 nm. Dissolution pores vary from 100 nm to 100 μm. Residual intergranular pores range from 1 μm to 40 μm. Based on the fractal characteristics, pore system is divided into macropores (mainly >300 nm), mesopores (mainly 7–300 nm), and micropores (mainly <7 nm). Micropores are adsorb-fluid pores that do not contribute to the storage and percolation but contribute significantly to contrasting specific surface area. Mesopores represent bound-fluid pores and only contribute to total porosity but not to permeability. Macropores represent movable-fluid pores, contributing to both porosity and permeability. The content and heterogeneity of macropores control the quality of Chang 7 tight sandstone. When macropore volume is >12×10−3 mL/g, the continuous percolation network consists entirely of macropores, resulting in higher porosity and permeability of the reservoir. Moreover, reservoir physical properties show excellent correlation with macropore heterogeneity. These results demonstrate that the content and heterogeneity of macropores are key indicators indicating the quality of the Chang 7 tight sandstones. |
| first_indexed | 2024-03-08T00:46:31Z |
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| language | English |
| last_indexed | 2024-03-08T00:46:31Z |
| publishDate | 2024-02-01 |
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| series | Frontiers in Earth Science |
| spelling | doaj.art-d0c51cba73a1402692eb7dc5976d46482024-02-15T10:07:57ZengFrontiers Media S.A.Frontiers in Earth Science2296-64632024-02-011210.3389/feart.2024.13610521361052Clarifying the contribution of multiscale pores to physical properties of Chang 7 tight sandstones: insight from full-scale pore structure and fractal characteristicsZhen Li0Zhen Li1Yilin Ren2Rui Chang3Yuanli Zhang4Xuze Zhang5Weichao Tian6Research Institute of Exploration and Development, PetroChina Changqing Oilfield Company, Xi’an, ChinaNational Engineering Laboratory for Exploration and Development of Low Permeability Oil and Gas Fields, Xi’an, ChinaResearch Institute of Exploration and Development, PetroChina Changqing Oilfield Company, Xi’an, ChinaResearch Institute of Exploration and Development, PetroChina Changqing Oilfield Company, Xi’an, ChinaResearch Institute of Exploration and Development, PetroChina Changqing Oilfield Company, Xi’an, ChinaResearch Institute of Exploration and Development, PetroChina Changqing Oilfield Company, Xi’an, ChinaHubei Key Laboratory of Petroleum Geochemistry and Environment, Yangtze University, Wuhan, ChinaThe pore structure and its heterogeneity of tight reservoirs are key factors affecting the storage and percolation of crude oil. The pore system of Chang 7 tight sandstone has multi-scale and multi-type characteristics. However, the contribution of different pore types and pore sizes to the physical properties of Chang 7 tight sandstone is still unclear. In this paper, we collected a suite of Chang 7 tight sandstones to investigate the full-scale pore structure and fractal characteristics by casting thin section, field emission scanning electron microscope, two-dimensional multi-scale backscattered scanning electron microscopy, N2 adsorption (NA) and NMR. The pore diameters of Chang 7 tight sandstone are usually distributed between 0.001 and 20 μm. Intercrystalline pores are mainly distuibuted <500 nm. Dissolution pores vary from 100 nm to 100 μm. Residual intergranular pores range from 1 μm to 40 μm. Based on the fractal characteristics, pore system is divided into macropores (mainly >300 nm), mesopores (mainly 7–300 nm), and micropores (mainly <7 nm). Micropores are adsorb-fluid pores that do not contribute to the storage and percolation but contribute significantly to contrasting specific surface area. Mesopores represent bound-fluid pores and only contribute to total porosity but not to permeability. Macropores represent movable-fluid pores, contributing to both porosity and permeability. The content and heterogeneity of macropores control the quality of Chang 7 tight sandstone. When macropore volume is >12×10−3 mL/g, the continuous percolation network consists entirely of macropores, resulting in higher porosity and permeability of the reservoir. Moreover, reservoir physical properties show excellent correlation with macropore heterogeneity. These results demonstrate that the content and heterogeneity of macropores are key indicators indicating the quality of the Chang 7 tight sandstones.https://www.frontiersin.org/articles/10.3389/feart.2024.1361052/fullfull-scale pore structurefractal characteristicsphysical propertiesNMRChang 7 tight sandstone |
| spellingShingle | Zhen Li Zhen Li Yilin Ren Rui Chang Yuanli Zhang Xuze Zhang Weichao Tian Clarifying the contribution of multiscale pores to physical properties of Chang 7 tight sandstones: insight from full-scale pore structure and fractal characteristics Frontiers in Earth Science full-scale pore structure fractal characteristics physical properties NMR Chang 7 tight sandstone |
| title | Clarifying the contribution of multiscale pores to physical properties of Chang 7 tight sandstones: insight from full-scale pore structure and fractal characteristics |
| title_full | Clarifying the contribution of multiscale pores to physical properties of Chang 7 tight sandstones: insight from full-scale pore structure and fractal characteristics |
| title_fullStr | Clarifying the contribution of multiscale pores to physical properties of Chang 7 tight sandstones: insight from full-scale pore structure and fractal characteristics |
| title_full_unstemmed | Clarifying the contribution of multiscale pores to physical properties of Chang 7 tight sandstones: insight from full-scale pore structure and fractal characteristics |
| title_short | Clarifying the contribution of multiscale pores to physical properties of Chang 7 tight sandstones: insight from full-scale pore structure and fractal characteristics |
| title_sort | clarifying the contribution of multiscale pores to physical properties of chang 7 tight sandstones insight from full scale pore structure and fractal characteristics |
| topic | full-scale pore structure fractal characteristics physical properties NMR Chang 7 tight sandstone |
| url | https://www.frontiersin.org/articles/10.3389/feart.2024.1361052/full |
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