Key Laboratory for the Study of Focused Magmatism and Giant Ore Deposits MLR

Fengcheng, China

Key Laboratory for the Study of Focused Magmatism and Giant Ore Deposits MLR

Fengcheng, China
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Qin X.-L.,Chang'an University | Qin X.-L.,Key Laboratory for the Study of Focused Magmatism and Giant Ore Deposits MLR | Li R.-X.,Chang'an University | Li R.-X.,Key Laboratory for the Study of Focused Magmatism and Giant Ore Deposits MLR | And 8 more authors.
Natural Gas Geoscience | Year: 2017

The Upper Palaeozoic gas reservoirs in the eastern Ordos Basin are typical tight sandstone reservoir. Petrographic observation and geochemical analysis were used to study diagenesis and diagenetic fluid of sandstone. Results show that two periods of altered mineral assemblages were formed after strong alteration. Early period of altered mineral assemblage includes kaolinite, flaky illites, sericite and quartz, which were altered by organic acidic fluid produced by thermal evolution of coal-measure source rock. Late period of altered mineral assemblage includes illite, epidote, ankerite, and idiomorphic pyriteetc. The δ13CPDB values of carbonate cement are from -1.18‰ to -11.97‰, with average of -5.57‰, and the δ18OPDB values are from -2.28‰ to -15.1‰ with average of -12.57‰. Illite and kaolinte are enriched in LREE but depleted in HREE characterized by downwards sloping and some extent of δEu and δCe anomaly. The peak homogenization temperature of fluid inclusions in late siliceous cements is 170℃, which is much higher than temperature of the maximum burial depth of strata. In early Cretaceousthe, Ordos Basin subsided. Meanwhile, a large-scale thermal anomaly event happened, which had facilitated the large scale hydrocarbon-generation of the Paleozoic coal-measure source rocks. The generated hydrocarbon fluid and hydrothermal fluid migrated into reservoir sandstone beds to alter the reservoir sandstone. Abundant of hydrothermal altered minerals were formed to fill pore space of reservoir sandstone which make reservoir compact. © 2017, Science Press. All right reserved.

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