Pore Structure and Fractal Character of Lacustrine Oil-Bearing Shale from the Dongying Sag, Bohai Bay Basin, China
To better understand the pore structure and fractal character of lacustrine shales and their influence on liquid hydrocarbon occurrences, in this study, a total of 29 lacustrine oil-bearing shale samples collected from the Shahejie Formation in the Dongying Sag, Bohai Bay Basin, were investigated ba...
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| Format: | Article |
| Language: | English |
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Wiley
2021-01-01
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| Series: | Geofluids |
| Online Access: | http://dx.doi.org/10.1155/2021/9945494 |
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| author | Pengfei Zhang Shuangfang Lu Zhiping Zeng Xiangchun Chang Junqian Li Guo Chen Junjian Zhang Zizhi Lin Jijun Li |
| author_facet | Pengfei Zhang Shuangfang Lu Zhiping Zeng Xiangchun Chang Junqian Li Guo Chen Junjian Zhang Zizhi Lin Jijun Li |
| author_sort | Pengfei Zhang |
| collection | DOAJ |
| description | To better understand the pore structure and fractal character of lacustrine shales and their influence on liquid hydrocarbon occurrences, in this study, a total of 29 lacustrine oil-bearing shale samples collected from the Shahejie Formation in the Dongying Sag, Bohai Bay Basin, were investigated based on nitrogen adsorption (NGA) analysis combined with TOC, Rock-Eval pyrolysis, X-ray diffraction (XRD), and field emission-scanning electron microscopy (FE-SEM) experiments. The relationships among the compositions (TOC, minerals, and oil content), pore structures, and fractal dimensions of the lacustrine shale samples were discussed. The results showed that the adsorption and fractal characteristics of lacustrine oil-bearing shales differ at relative pressures of 0-0.1 and 0.5-1. Two corresponding fractal dimensions D1 and D2 were determined by the FHH model according to the nitrogen adsorption branches. Specifically, D1 varies from 2.4292 to 2.6109 (mean 2.5245), and D2 varies between 2.4680 and 2.8535 (mean 2.6889). The specific surface area (SSA) ranges from 1.512 m2/g to 34.002 m2/g, with an average of 13.656 m2/g, the total pore volume is between 6.0 × 10-3 cm3/g and 48.4 × 10-3 cm3/g (mean 24.5 × 10-3 cm3/g), and the average pore diameter is in the range of 4.22 nm to 19.57 nm (mean 9.35 nm). Both D1 and D2 increase with increasing SSA and increase with decreasing average pore diameters but have no correlation with pore volume. Moreover, D1 and D2 exhibit positive relationships with clay minerals and negative correlations with carbonate minerals (calcite and dolomite). The relationship between fractal dimensions (D1 and D2) and TOC contents is expressed as a U-shaped curve, characterized by the minimum D values at approximately 3% TOC. The shale oil content is controlled by the pore structures and fractal dimensions, and lacustrine shales with lower SSAs and smaller fractal dimensions would have more free oil. Therefore, lacustrine shales in the oil window with TOC contents ranging from 2% to 4% are probably the preferred shale oil exploration target in the Shahejie Formation, Dongying Sag, Bohai Bay Basin. The results indicate that fractal analysis can provide insight into the pore structure characteristics and oil storage capacity of lacustrine shales. |
| format | Article |
| id | doaj-art-f29ebedbaa084b56908c212dc2e64bf8 |
| institution | OA Journals |
| issn | 1468-8115 1468-8123 |
| language | English |
| publishDate | 2021-01-01 |
| publisher | Wiley |
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| series | Geofluids |
| spelling | doaj-art-f29ebedbaa084b56908c212dc2e64bf82025-08-20T02:21:58ZengWileyGeofluids1468-81151468-81232021-01-01202110.1155/2021/99454949945494Pore Structure and Fractal Character of Lacustrine Oil-Bearing Shale from the Dongying Sag, Bohai Bay Basin, ChinaPengfei Zhang0Shuangfang Lu1Zhiping Zeng2Xiangchun Chang3Junqian Li4Guo Chen5Junjian Zhang6Zizhi Lin7Jijun Li8College of Earth Science and Engineering, Shandong University of Science and Technology, Qingdao, 266590 Shandong, ChinaKey Laboratory of Deep Oil and Gas, China University of Petroleum (East China), Qingdao, 266580 Shandong, ChinaResearch Institute of Exploration and Development, Shengli Oilfield Company, Sinopec, Dongying, 257000 Shandong, ChinaCollege of Earth Science and Engineering, Shandong University of Science and Technology, Qingdao, 266590 Shandong, ChinaKey Laboratory of Deep Oil and Gas, China University of Petroleum (East China), Qingdao, 266580 Shandong, ChinaCollege of Earth Science and Engineering, Shandong University of Science and Technology, Qingdao, 266590 Shandong, ChinaCollege of Earth Science and Engineering, Shandong University of Science and Technology, Qingdao, 266590 Shandong, ChinaKey Laboratory of Deep Oil and Gas, China University of Petroleum (East China), Qingdao, 266580 Shandong, ChinaKey Laboratory of Deep Oil and Gas, China University of Petroleum (East China), Qingdao, 266580 Shandong, ChinaTo better understand the pore structure and fractal character of lacustrine shales and their influence on liquid hydrocarbon occurrences, in this study, a total of 29 lacustrine oil-bearing shale samples collected from the Shahejie Formation in the Dongying Sag, Bohai Bay Basin, were investigated based on nitrogen adsorption (NGA) analysis combined with TOC, Rock-Eval pyrolysis, X-ray diffraction (XRD), and field emission-scanning electron microscopy (FE-SEM) experiments. The relationships among the compositions (TOC, minerals, and oil content), pore structures, and fractal dimensions of the lacustrine shale samples were discussed. The results showed that the adsorption and fractal characteristics of lacustrine oil-bearing shales differ at relative pressures of 0-0.1 and 0.5-1. Two corresponding fractal dimensions D1 and D2 were determined by the FHH model according to the nitrogen adsorption branches. Specifically, D1 varies from 2.4292 to 2.6109 (mean 2.5245), and D2 varies between 2.4680 and 2.8535 (mean 2.6889). The specific surface area (SSA) ranges from 1.512 m2/g to 34.002 m2/g, with an average of 13.656 m2/g, the total pore volume is between 6.0 × 10-3 cm3/g and 48.4 × 10-3 cm3/g (mean 24.5 × 10-3 cm3/g), and the average pore diameter is in the range of 4.22 nm to 19.57 nm (mean 9.35 nm). Both D1 and D2 increase with increasing SSA and increase with decreasing average pore diameters but have no correlation with pore volume. Moreover, D1 and D2 exhibit positive relationships with clay minerals and negative correlations with carbonate minerals (calcite and dolomite). The relationship between fractal dimensions (D1 and D2) and TOC contents is expressed as a U-shaped curve, characterized by the minimum D values at approximately 3% TOC. The shale oil content is controlled by the pore structures and fractal dimensions, and lacustrine shales with lower SSAs and smaller fractal dimensions would have more free oil. Therefore, lacustrine shales in the oil window with TOC contents ranging from 2% to 4% are probably the preferred shale oil exploration target in the Shahejie Formation, Dongying Sag, Bohai Bay Basin. The results indicate that fractal analysis can provide insight into the pore structure characteristics and oil storage capacity of lacustrine shales.http://dx.doi.org/10.1155/2021/9945494 |
| spellingShingle | Pengfei Zhang Shuangfang Lu Zhiping Zeng Xiangchun Chang Junqian Li Guo Chen Junjian Zhang Zizhi Lin Jijun Li Pore Structure and Fractal Character of Lacustrine Oil-Bearing Shale from the Dongying Sag, Bohai Bay Basin, China Geofluids |
| title | Pore Structure and Fractal Character of Lacustrine Oil-Bearing Shale from the Dongying Sag, Bohai Bay Basin, China |
| title_full | Pore Structure and Fractal Character of Lacustrine Oil-Bearing Shale from the Dongying Sag, Bohai Bay Basin, China |
| title_fullStr | Pore Structure and Fractal Character of Lacustrine Oil-Bearing Shale from the Dongying Sag, Bohai Bay Basin, China |
| title_full_unstemmed | Pore Structure and Fractal Character of Lacustrine Oil-Bearing Shale from the Dongying Sag, Bohai Bay Basin, China |
| title_short | Pore Structure and Fractal Character of Lacustrine Oil-Bearing Shale from the Dongying Sag, Bohai Bay Basin, China |
| title_sort | pore structure and fractal character of lacustrine oil bearing shale from the dongying sag bohai bay basin china |
| url | http://dx.doi.org/10.1155/2021/9945494 |
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