Ca/Mg Ratio Estimation of the Dolomitizing Fluids in Triassic Feixianguan Formation, Northeastern Sichuan Basin
详细信息
- 责任者：Hu Zuowei (State Key Laboratory of Oil/Gas Reservoir Geology and Exploitation ; Institute of Sedimentary Geology ; Chengdu University of Technology ; Chengdu 610059 ; China) ; Huang Sijing
- 刊名：Acta Geologica Sinica
- 出版年：2012
- 卷期：87(1)
- 关键词：碳酸盐岩储集层 ; carbonate reservoirs ; 白云石化 ; dolomitization ; 四川 ; Sichuan Province
- 页码：p.110-118
- 图表：illus., 1 table, 47 refs.
- 分类号：1003
- issnNo：ISSN0001-5717
- isbnNo：CN11-1951/P
摘要
Grainy dolomite and crystalline dolomite are the most important natural gas reservoir rocks of the Triassic Feixianguan Formation in the northeastern Sichuan basin,but their origins have long been the focus of research for sedimentologists and petroleum geologists.Based on the formation temperatures of different types of dolomites in the Triassic Feixianguan Formation,and the relationship between the temperatures and Ca/Mg ratios of the dolomitizing fluid,this paper obtained the main distribution pattern of Ca/Mg ratios of dolomitizing fluids.The results show that the Ca/Mg ratios of the dolomitizing fluids correspond to different types of dolomites.It is also confirmed that the Ca/Mg ratios of Triassic seawater or related sea-derived fluids,and of mixing fluids of both Triassic fluid and meteoric water are in accord with requirements of dolomitization or dolomite precipitation at temperature ranges from 40℃ to 130℃,or even higher temperature.The micrite dolomite and grainy dolomite(with original texture) could be related to relatively rapid precipitation at a low temperature from the surface or near-surface mixing-fluids with low Ca/Mg ratios,and these dolomites are relatively fine and anhedral.The crystalline dolomite(including the transitional rock types with the similar texture and dolomite cement) could be related to relatively slow precipitation at high temperature from the burial Triassic seawater or related fluids with high Ca/Mg ratio,and these dolomites are relatively coarse and euhedral.The Ca/Mg ratio estimation of the dolomitizing fluids will provide some valuable basic data to the studies of the high-quality dolomite reservoirs in the Triassic Feixianguan Formation,northeastern Sichuan basin.