| Kinetic Modeling of Diagenesis of Eogene Lacustrine Sandstone Reservoirs in the Jianghan Basin,Southeastern China |
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| 作者姓名： | 倪师军 卿海若 唐建武 周美夫 李泽琴 |
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| 作者单位： | [1]ChengduUniversityofTechnology,Chengdu610059,China [2]DepartmentofGeology,UniveristyofSaskatchewan,ReginaSK,CanadaS4S0A2,Canada |
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| 基金项目： | 国家自然科学基金，State Education Commission of China |
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| 摘 要： | In the Tuoshi oilfield,located in the Cenozoic Jianghan Basin of southeastern China ,there have been found hydrocarbon reservoirs hosted in lacustrine sandstones of the Eogene Xingouzui Formation.The main diagenetic features identified in these sandstones include the dissolution of detrital K-feldspar and albite grains,the precipitation of quartz as overgrowths and /or cements ,and the precipitation and /or transformation of clay minerals.These diagenetic features were interpreted to have occurred in early,intermediate and late stages,based on the burial depth.The kinetics of fluid-mineral reactions and the concentrations of aqueous species au each stage of diagenesis were simulated numerically for these lacustrine sandstones,using a quasi-sta-tionary state approximation that incorporates simultaneous chemical reactions in a time-space continuum.During the early diagenetic stage,pore fluid was weakly acidic,which resulted in dissolution of K-feldspar and albite and,therefore,led to the release of K^ ,Na^ ,Al^3 and SiO2(aq) into the diagenetic fluid.The increased K^ ,Na^ ,Al^3 and SiO2(aq) concentrations in the diagenetic fluid caused the precipitation of quartz,kaolinite and illite.At the beginning of the intermediate diagenetic stage the concentration of H^ was built up due to the decomposition of organic matter,which was responsible for further dissolution of K-feldspar and albite and pre-cipitation of quartz,kaolinite,and illite.During the late diagenetic stage,the pore fluid was weakly alkaline,K-feldspar became stable and was precipitated with quartz and clay minerals.When the burial depth was greater than 3000 m,the pore fluids became supersaturated with respect to allbite,but undersaturated with respect to quartz,resulting in the precipitation of albite and the dissolution of quartz.The diagenetic reactions forecasted in the numerical modeling closely matched the diagenet-ic features identified by petrographic examination, and therefore,can help us to gain a better understanding of the diagenetic processes and associated porosity evolution in sandstone reservoirs.
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| 关 键 词： | 成岩作用 动力学模型 成岩流体 湖成沙岩 江海盆地 地球化学 |
Kinetic modeling of diagenesis of Eogene lacustrine sandstone reservoirs in the Jianghan Basin, southeastern China |
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| Ni Shijun,Qing Hairuo,Tang Jianwu,Zhou Meifu,Li Zeqin.Kinetic Modeling of Diagenesis of Eogene Lacustrine Sandstone Reservoirs in the Jianghan Basin,Southeastern China[J].Chinese Journal of Geochemistry,2002,21(4):298-307. |
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| Authors: | Ni Shijun Qing Hairuo Tang Jianwu Zhou Meifu Li Zeqin |
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| Institution: | (1) Chengdu University of Technology, 610059 Chengdu, China;(2) Department of Geology, University of Saskatchewan, Canada S4S 0A2 Regina, SK, Canada;(3) Department of Ocean, Earth & Atmospheric Sciences, Old Dominion University, 23529-0267 Norfolk, VA, USA;(4) Department of Earth Sciences, University of Hong Kong, Pokfulam Road, Hong Kong, China |
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| Abstract: | In the Tuoshi oilfield, located in the Cenozoic Jianghan Basin of southeastern China, there have been found hydrocarbon reservoirs
hosted in lacustrine sandstones of the Eogene Xingouzui Formation. The main diagenetic features identified in these sandstones
include the dissolution of detrital K-feldspar and albite grains, the precipitation of quartz as overgrowths and/or cements,
and the precipitation and/or transformation of clay minerals. These diagenetic features were interpreted to have occurred
in early, intermediate and late stages, based on the burial depth.
The kinetics of fluid-mineral reactions and the concentrations of aqueous species at each stage of diagenesis were simulated
numerically for these lacustrine sandstones, using a quasi-stationary state approximation that incorporates simultaneous chemical
reactions in a time-space continuum. During the early diagenetic stage, pore fluid was weakly acidic, which resulted in dissolution
of K-feldspar and albite and, therefore, led to the release of K+, Na+, Al3+ and SiO2(aq) into the diagenetic fluid. The increased K+, Na+, Al3+ and SiO2(aq) concentrations in the diagenetic fluid caused the precipitation of quartz, kaolinite and illite. At the beginning of the
intermediate diagenetic stage the concentration of H+ was built up due to the decomposition of organic matter, which was responsible for further dissolution of K-feldspar and
albite and precipitation of quartz, kaolinite, and illite. During the late diagenetic stage, the pore fluid was weakly alkaline,
K-feldspar became stable and was precipitated with quartz and clay minerals. When the burial depth was greater than 3000 m,
the pore fluids became supersaturated with respect to albite, but undersaturated with respect to quartz, resulting in the
precipitation of albite and the dissolution of quartz.
The diagenetic reactions forecasted in the numerical modeling closely matched the diagenetic features identified by petrographic
examination, and therefore, can help us to gain a better understanding of the diagenetic processes and associated porosity
evolution in sandstone reservoirs.
This project was funded by the National Natural Science Foundation of China (Grant No. 49133080), and by the Trans-century
Training Programme Foudation for the Talents sponsored by the State Education Commission of China. |
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| Keywords: | kinetic modeling of diagenesis diagenetic fluid geochemistry lacustrine sandstone reservoir Jianghan Basin |
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