New evidence for the genesis of Qixia Formation dolomites in the western Sichuan Basin: Geochemical characteristics of rare earth elements

被引：0
|
作者：
Ma H. [1 ]
Su Z. [1 ,2 ]
Liang R. [1 ,3 ]
Fang J. [4 ]
Lin L. [1 ,2 ]
机构：
[1] Institute of Sedimentary Geology, Chengdu University of Technology, Chengdu
[2] State Key Laboratory of Oil & Gas Reservoir Geology and Exploitation, Chengdu University of Technology, Chengdu
[3] Institute of Petroleum Exploration and Development, Sinopec Zhongyuan Oilfield Company, Puyang
[4] Technical Innovation Center for Shale Gas Exploration and Development in Complex Structural Areas, Ministry of Natural Resources, Chengdu
来源：
Natural Gas Industry | 2021年 / 41卷 / 12期
关键词：
Dolomite genesis; Dolomite reservoir; Fluid origin; Geochemistry; Middle Permian Qixia Formation; Rare earth element; Western Sichuan Basin; Y/Ho ratio;
D O I：
10.3787/j.issn.1000-0976.2021.12.006
中图分类号：
学科分类号：
摘要：
Practical exploration and development prove that Middle Permian Qixia Formation dolomites in the western Sichuan Basin are important reservoir rocks, but their genesis is still controversial. In order to clarify the genesis of Qixia Formation dolomites in this area and provide a basis for searching for high-quality dolomite reservoirs, this paper takes the typical field profiles and drilling core samples of Qixia Formation in the western Sichuan Basin as the research objects to discuss the relationships between dolomitic fluid and seawater and Emeishan basalt by analyzing petrology, rare earth element pattern and Y/Ho ratio. And the following research results are obtained. First, Qixia Formation dolomites can be classified into four types, including crystalline grain dolomites, residual grain dolomites, saddle dolomites and vein dolomites. Second, the rare earth element pattern and Y/Ho ratio of crystalline grain dolomites and residual grain dolomites have the characteristics of marine fluid, and the δEu value is higher, which might be the result of the high temperature effect induced by the eruption of Emeishan basalt. Third, the genesis of saddle dolomites and vein dolomites is related to the distance from the Emeishan eruption zone. The rare earth element pattern and Y/Ho ratio of saddle dolomites and vein dolomites near the Emeishan eruption zone are close to those of Emeishan basalt, and the δEu is higher than 1, which suggests that the dolomites are of hydrothermal genesis related to the eruption event of Emeishan basalt. The rare earth element pattern and Y/Ho ratio of saddle dolomites and vein dolomites far from the Emeishan eruption zone have the characteristics of marine fluid, which indicates that the dolomites are formed by the filling of seawater along pores after being heated by high-temperature fluid in the period of shallow burial. In conclusion, Qixia Formation dolomites in the western Sichuan Basin are mainly of shallow burial genesis, but due to the reworking of thermal events, the superimposition zone of the marginal platform along the northwestern margin of the Sichuan Basin and the outer zone of Emeishan igneous province is the favorable reservoir facies belt, and the hydrothermal dolomites developed along the southwestern margin are not favorable for hydrocarbon accumulation. © 2021, Natural Gas Industry Journal Agency. All right reserved.
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页码：49 / 59
页数：10
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