| 华北地台东部下古生界白云岩的类型及储集性 |
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| 引用本文： | 金振奎,冯增昭.华北地台东部下古生界白云岩的类型及储集性[J].沉积学报,1993,11(2):11-18. |
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| 作者姓名： | 金振奎 冯增昭 |
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| 作者单位： | 石油大学, 北京 |
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| 摘 要： | 华北地台东部下古生界的白云岩可分为泥-粉晶白云岩和细-粗晶白云岩。前者包括含石膏的和不含石膏的;后者包括等晶粒的和不等晶粒的,含石膏的和不含石膏的泥-粉晶白云岩分别是干旱和潮湿气候潮上带蒸气发泵浓缩白云化的产物;等晶粒细-粗晶白云岩主要分布于平行不整合面之下,乃混合水白云化之产物;不等晶粒细-粗晶白云岩由早期的白云岩重结晶形成。 白云岩中的孔隙类型多样,其储集性受白云石含量和颗粒大小以及粘土含量等因素影响。
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| 关 键 词： | 华北地台 下古生界 白云岩类型 储集性 |
| 收稿时间： | 1991-05-11 |
Types and Reservoiring Performance of Dolostones of the Lower Paleozoic in Eastern North-China Platform |
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| Institution: | University of Petroleum,Beijing |
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| Abstract: | Dolostones are very common in the Lower Paleozoic of eastern North-China Platform, and can be divided into mud-silt-sized crystalline dolostones and fine-coarse crystalline dolostones. The former includes gypsiferous and non-gypsiferous; the later includes equal-crystal and unequal-crystal fine-coarse crystalline dolostones. Gypsiferous mud-silt-sized crystalline dolostones are well laminated,show bird's-eyes and mudcracks,contain gypsum crystals or nodules,and are associated with chicken-wire or laminated gypsum rocks. Based on the analysis of two samples,their δ13C is 0. 42‰-2. 21‰, average 1. 13‰(PDB) ;δ18O is -6. 01‰-4. 77‰, average -5. 39‰(PDB). The low δ18O results from recrystallization in fresh water and/or under high temperatures. These dolostones are similar to the Sabkha penecontemporaneous dolostones in the Persian Gulf,and are formed in supratidal flats by evaporative pumping dolomitizatiom under arid climate. Non-gypsiferous mud-silt -sized crystalline dolostones are similar to the gypsiferous ones in texture and structure, but do not contain gypsum and are not associated with gypsum rocks. Based on the analysis of 17 samples,their δ13C is -3. 69‰-3. 41‰,average 0. 03‰;δ18O - 8. 17‰-4. 04‰,average -5. 91‰. The low δ18O also results from recrystallization in fresh water and/or under high temperatures. These dolostones are similar to the supralittoral penecontemporaneous dolostones on the Bahamian Platform, and are formed in supratidal flats by evaporative pumping dolomitization under humid climate. Equal-crystal fine to coarse crystalline dolostones are composed of dolomites of basically the same size. Euhedral and semi-euhedral dolomites are common,especially when dolomitization is incomplete. Some dolomites show dirty centers and clean marging,and may contaim calcite inclusions. Thses dolomites are formed directly by replacing limestones. Based on analysis of 15 samples,the δ13C is -2. 11‰-2. 10‰,average -0. 40‰;δ18O -8. 49‰-4. 09‰,average -5. 53‰. These dolostones are mostly distributed under the disconformity between the Lower and Middle Ordovician,and are formed by dorag dolomitization. Unequal-crystal fine-coarse crystalline dolostones are composed of dolomites of greatly different size. The dolomites are commonly anhedral. Based on analysis of 5 samples,the 513C is -4. 72‰～-1.08‰,average -2. 83‰;δ18O - 9. 27‰～- 7. 32‰, average -8. 31‰. These dolostones are formed by recrystallization of earlier dolostones in fresh water. Porosities of dolostones in the Lower Paleozoic can be divided into intracrystal pores,in-tercrystal pores,vugs,cast pores,fissures,bird's-eye pores and shrinking fissures. The reser-voiring performance of the dolostones are controlled by many factors,such as the content and size of dolomites,and clay content of the dolostones, non-clayey silt-sized crystalline dolostones show the best reservoiring performance. |
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