You are here: Home » Past Issues » Volume 10, 2015 - Number 2 » STRUCTURALLY CONTROLLED DEEP HYDROTHERMAL TRANSFORMATION OF ORDOVICIAN CARBONATE RESERVOIRS, CENTRAL TARIM BASIN, NW CHINA
Zhuang RUAN1, Bingsong YU1, Jia MA2 & Yinlu PAN1
1State Key Laboratory of Geological Process and Mineral Resources, China University of Geosciences, Beijing 100083, China. Ruanz0103@cugb.edu.cn
2Beijing Research Institute of Chemical Engineering and Metallurgy, CNNC, Beijing 101149, China.
STRUCTURALLY CONTROLLED DEEP HYDROTHERMAL TRANSFORMATION OF ORDOVICIAN CARBONATE RESERVOIRS, CENTRAL TARIM BASIN, NW CHINA
Ordovician carbonate rock is an important hydrocarbon reservoir in the Tarim Basin of NW China. Secondary reservoir space and cementation are related to deep fluid activity, particularly magmatic hydrothermal fluid. Classification and modeling of the magmatic hydrothermal fluids is important in the identification of high-grade reservoirs. The presence of many anomalously a high-temperature fluid inclusion is indicative of significant hydrothermal activity. Samples from both filling (carbonate or other minerals filled in cracks and dissolution holes of carbonate rocks) and country rocks were collected and their C, O, and Sr isotope ratios analyzed. Filling samples were found to have low δ13C and δ18O values, and high 87Sr/86Sr values. These samples are distinct from the country rocks and other filling samples, indicating the presence of magmatic hydrothermal fluids. Trace element abundance was analyzed in 11 filling samples, yielding positive Eu anomalies and high Th/U values in some samples. Conduit systems such as unconformities, faults, and cracks limit the distribution of hydrothermal fluid and give it a distinct trace elemental and isotopic signature. The hydrothermal fluid derived from magmatic activity may have caused dissolution, cementation, and an increase in the formation fluid temperature.
Keyword: Hydrothermal Fluid, Ordovician Carbonate Reservoir, Tarim Basin, Isotopes, Trace elements
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