Characteristics and origin of dolostones in the Miocene Meishan Formation in Well Xike 1, Xisha Islands, South China Sea

被引：0
|
作者：
Yin H. [1 ]
Wang Y. [2 ]
Liu J. [2 ]
Shi Z. [1 ]
Zhang D. [2 ]
机构：
[1] Institute of Sedimentary Geology, Chengdu University of Technology, Chengdu, 610059, Sichuan
[2] Zhanjiang Branch of CNOOC(China), Zhanjiang, 524057, Guangdong
来源：
Oil and Gas Geology | 2020年 / 41卷 / 01期
关键词：
Dolostone; Geochemistry; Meishan Formation; Miocene; Petrological characteristics; South China Sea;
D O I：
10.11743/ogg20200119
中图分类号：
学科分类号：
摘要：
Cenozoic carbonate platform was well developed in South China Sea, and dolostones are quite common in carbonate sequences of Xisha Islands. The characteristics of the Miocene Meishan dolomite is described by studying the macro-and micro-scopic features of dolostones, the carbon and oxygen isotopes, and main/trace elements in Well Xike 1. Mainly four categories of dolostones were developed in the Meishan Formation in Well Xike 1, which are different in thickness, color and porosity. Sucrosic dolomites, commonly distributed under the ancient exposed surface, can be seen in thick-bedded dolostones. While thin-bedded dolostones feature loose consolidation and incomplete dolomitization.The dolomite crystals are dominated by subhedral-idiomorphic flat surfaces, and bright edge and foggy center are seen in some dolomites of very fine to fine-crystallized crystals. The carbon and oxygen isotopes of carbonate rocks in the Meishan Formation show certain correlation, while the correlation of carbon and oxygen isotopic values in the dolostones is insignificant. The paleosalinity value of dolostones is calculated to be slightly higher than that of contemporaneous seawater. The oxygen isotopic value of dolostones is positive, indicating that the dolomitization was not affected by magmatic hydrothermal fluids and organic acid solution.Most thin-bedded dolomites in the Meishan Formation are calcareous dolostones, low in Fe, Sr and Mn concentrations, suggesting that the source of magnesium ions is mainly seawater. The rare earth elements (REE) are characterized by low Ce and Eu. In conclusion, the dolomitization in the study might have been caused by seepage reflux, and is characterized by high porosity and permeability as a result of geothermal warming, implying good reservoir potential. © 2020, OIL & GAS GEOLOGY Editorial Board. All right reserved.
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页码：209 / 222
页数：13
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