Modification of dolomitization on reservoir spaces in reef–shoal complex: A case study of Permian Changxing Formation, Sichuan Basin, SW China
The porosity of the reef–shoal complex increases with the increase of dolomite content, and it is worth investigating whether dolomitization leads to the formation of new pores or maintains the original porosity. The reef–shoal complex of the Permian Changxing Formation in the Sichuan Basin is selec...
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De Gruyter
2024-12-01
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| Series: | Open Geosciences |
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| Online Access: | https://doi.org/10.1515/geo-2022-0734 |
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| author | Zhang Qiang Liu Lizhi Song Honglu Jin Chaosu Qiao Na Qi Lin |
| author_facet | Zhang Qiang Liu Lizhi Song Honglu Jin Chaosu Qiao Na Qi Lin |
| author_sort | Zhang Qiang |
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| description | The porosity of the reef–shoal complex increases with the increase of dolomite content, and it is worth investigating whether dolomitization leads to the formation of new pores or maintains the original porosity. The reef–shoal complex of the Permian Changxing Formation in the Sichuan Basin is selected to reveal the modification effect of dolomitization on the reef–shoal complex. As important reservoirs of hydrocarbons and carbon dioxide, reef–shoal complexes are composed of grainstone and framestone on both sides of the Kaijiang-Liangping Trough during the Late Permian. The difference in the development degree of sparry calcite cement determines whether the framestone on both sides of the Trough undergoes dolomitization or not. When the Mg2+ supply is insufficient, the dolomitization fluid prioritizes the replacement of the lime mud matrix. When the Mg2+ supply is sufficient, the reef-building organisms and bioclastic grains are completely replaced by dolomite. Statistical results show that when the dolomite content increases from 0 to 40%, there is no significant change in porosity. When dolomite content increases from 40 to 60%, the porosity gradually increases slightly. When dolomite content exceeds 60% and continues to increase, the porosity increases sharply. For reef–shoal complex reservoirs, dolomitization did not lead to the formation of new pores, but effectively preserved primary intergranular pores and freshwater leaching-induced pores. The porosity increases with the increase of dolomite content, partly due to pore preservation and partly due to the more effective anticompaction (and pressure solution) effect of dolomite compared to calcite, reflecting the overall effect of dolomite pore preservation. Although early freshwater leaching played a positive role in the formation of dolomite reservoirs, the preservation effect of dolomite pores contributes more to the current porosity and permeability of reservoirs, resulting in the highest quality reservoirs of reef–shoal complexes often developing at a certain distance below the exposed surface, and the best reservoir is dolomite in the upper part of the reef–shoal complexes, rather than dolomite interval located at the top. |
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| institution | Kabale University |
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| language | English |
| publishDate | 2024-12-01 |
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| spelling | doaj-art-370b5ebd583a41bfaeeecb7629fdf7b12024-12-10T07:31:15ZengDe GruyterOpen Geosciences2391-54472024-12-0116118110.1515/geo-2022-0734Modification of dolomitization on reservoir spaces in reef–shoal complex: A case study of Permian Changxing Formation, Sichuan Basin, SW ChinaZhang Qiang0Liu Lizhi1Song Honglu2Jin Chaosu3Qiao Na4Qi Lin5Shandong Shengli Vocational College, Dongying, Shandong, 257100, ChinaShandong Shengli Vocational College, Dongying, Shandong, 257100, ChinaCNOOC Experimental Center, CNOOC EnerTech-Drilling & Production Company, Tianjin, 300480, ChinaShandong Shengli Vocational College, Dongying, Shandong, 257100, ChinaShandong Shengli Vocational College, Dongying, Shandong, 257100, ChinaGeology Exploration and Development Research Institute, CNPC Chuanqing Drilling Engineering Co., Ltd., Chengdu, Sichuan, 610051, ChinaThe porosity of the reef–shoal complex increases with the increase of dolomite content, and it is worth investigating whether dolomitization leads to the formation of new pores or maintains the original porosity. The reef–shoal complex of the Permian Changxing Formation in the Sichuan Basin is selected to reveal the modification effect of dolomitization on the reef–shoal complex. As important reservoirs of hydrocarbons and carbon dioxide, reef–shoal complexes are composed of grainstone and framestone on both sides of the Kaijiang-Liangping Trough during the Late Permian. The difference in the development degree of sparry calcite cement determines whether the framestone on both sides of the Trough undergoes dolomitization or not. When the Mg2+ supply is insufficient, the dolomitization fluid prioritizes the replacement of the lime mud matrix. When the Mg2+ supply is sufficient, the reef-building organisms and bioclastic grains are completely replaced by dolomite. Statistical results show that when the dolomite content increases from 0 to 40%, there is no significant change in porosity. When dolomite content increases from 40 to 60%, the porosity gradually increases slightly. When dolomite content exceeds 60% and continues to increase, the porosity increases sharply. For reef–shoal complex reservoirs, dolomitization did not lead to the formation of new pores, but effectively preserved primary intergranular pores and freshwater leaching-induced pores. The porosity increases with the increase of dolomite content, partly due to pore preservation and partly due to the more effective anticompaction (and pressure solution) effect of dolomite compared to calcite, reflecting the overall effect of dolomite pore preservation. Although early freshwater leaching played a positive role in the formation of dolomite reservoirs, the preservation effect of dolomite pores contributes more to the current porosity and permeability of reservoirs, resulting in the highest quality reservoirs of reef–shoal complexes often developing at a certain distance below the exposed surface, and the best reservoir is dolomite in the upper part of the reef–shoal complexes, rather than dolomite interval located at the top.https://doi.org/10.1515/geo-2022-0734reefshoal complexdolomitizationdiagenetic sequencepore preservationchangxing formationsichuan basin |
| spellingShingle | Zhang Qiang Liu Lizhi Song Honglu Jin Chaosu Qiao Na Qi Lin Modification of dolomitization on reservoir spaces in reef–shoal complex: A case study of Permian Changxing Formation, Sichuan Basin, SW China Open Geosciences reef shoal complex dolomitization diagenetic sequence pore preservation changxing formation sichuan basin |
| title | Modification of dolomitization on reservoir spaces in reef–shoal complex: A case study of Permian Changxing Formation, Sichuan Basin, SW China |
| title_full | Modification of dolomitization on reservoir spaces in reef–shoal complex: A case study of Permian Changxing Formation, Sichuan Basin, SW China |
| title_fullStr | Modification of dolomitization on reservoir spaces in reef–shoal complex: A case study of Permian Changxing Formation, Sichuan Basin, SW China |
| title_full_unstemmed | Modification of dolomitization on reservoir spaces in reef–shoal complex: A case study of Permian Changxing Formation, Sichuan Basin, SW China |
| title_short | Modification of dolomitization on reservoir spaces in reef–shoal complex: A case study of Permian Changxing Formation, Sichuan Basin, SW China |
| title_sort | modification of dolomitization on reservoir spaces in reef shoal complex a case study of permian changxing formation sichuan basin sw china |
| topic | reef shoal complex dolomitization diagenetic sequence pore preservation changxing formation sichuan basin |
| url | https://doi.org/10.1515/geo-2022-0734 |
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