Hydrocarbon charging histories of the Ordovician reservoir in the Tahe oil field,Tarim Basin,China

The Ordovician reservoir of the Tahe oil field went through many tectonic reconstructions, and was charac-terized by multiple hydrocarbon chargings. The aim of this study was to unravel the complex charging histories. Systematicanalysis of fluid inclusions was employed to complete the investigation. Fluorescence observation of oil inclusions underUV light, and microthermometry of both oil and aqueous inclusions in 105 core samples taken from the Ordovician reservoirindicated that the Ordovician reservoir underwent four oil chargings and a gas charging. The hydrocarbon chargings oc-curred at the late Hercynian, the Indo-Sinian and Yanshan, the early Himalaya, the middle Himalaya, and the late Himalaya,respectively. The critical hydrocarbon charging time was at the late Hercynian.     

Hydrocarbon charging histories of the Ordovician reservoir in the Tahe oil field, Tarim Basin, China

INTRODUCTION Researches on hydrocarbon charging historyare essentially important to exploration and de-velopment, especially for the reservoirs subject tomultiple hydrocarbon generations, discharges, mi-grations and accumulations, as was the case of theOrdovician reservoir of the Tahe oil field located atthe southwest slope of the Akekule uplift, TarimBasin, China. Regarding the hydrocarbon charginghistories of the Ordovician reservoir, previousstudies based on burial histories (Y…     

Discovery of ultrahigh-T spinel-garnet granulite with pure CO2 fluid inclusions from the Altay orogenic belt, NW China

We first report discovery of the spinel-garnet-orthopyroxene granulite with pure CO2 fluid inclusions from the Fuyun region of the late Paleozoic Altay orogenic belt in Central Asia, NW China. The rock is characterized by an assemblage of garnet, orthopyroxene, spinel, cordierite, biotite, plagioclase and quartz. Symplectites of orthopyroxene and spinel,and orthopyroxene and cordierite indicate decompression under UHT conditions. Mineral chemistry shows that the orthopyroxenes have high XMg and Al2O3 contents (up to 9.23 wt%). Biotites are enriched in TiO2 and XMg and are stable under granulite facies conditions. The garnet and quartz from the rock carry monophase fluid inclusions which show peak melting temperatures of around -56.7 ℃, indicating a pure CO2 species being presented during the ultrahigh-T metamorphism in the Altay orogenic belt. The inclusions homogenize into a liquid phase at temperatures around 15.3-23.8℃ translating into CO2densities of the order of 0.86-0.88 g/cm3. Based on preliminary mineral paragenesis, reaction textures and petrogenetic grid considerations, we infer that the rock was subjected to UHT conditions. The CO2-rich fluids were trapped during exhumation along a clockwise P-T path following isothermal decompression under UHT conditions.     

Science Letters:Discovery of ultrahigh-T spinel-garnet granulite with pure CO_2 fluid inclusions from the Altay orogenic belt, NW China

We first report discovery of the spinel-garnet-orthopyroxene granulite with pure CO2 fluid inclusions from the Fuyun region of the late Paleozoic Altay orogenic belt in Central Asia, NW China. The rock is characterized by an assemblage of garnet, orthopyroxene, spinel, cordierite, biotite, plagioclase and quartz. Symplectites of orthopyroxene and spinel, and orthopyroxene and cordierite indicate decompression under UHT conditions. Mineral chemistry shows that the or-thopyroxenes have high XMg and A12O3 contents (up to 9.23 wt%). Biotites are enriched in TiO2 and XMg and are stable under granulite facies conditions. The garnet and quartz from the rock carry monophase fluid inclusions which show peak melting temperatures of around -56.7℃, indicating a pure CO2 species being presented during the ultrahigh-T metamorphism in the Altay orogenic belt. The inclusions homogenize into a liquid phase at temperatures around 15.3-23.8℃ translating into CO2 densities of the order of 0.86-0.88 g/cm3. Based on prelim     

Discovery of ultrahigh-T spinel-garnet granulite with pure CO<Subscript>2</Subscript> fluid inclusions from the Altay orogenic belt,NW China

We first report discovery of the spinel-garnet-orthopyroxene granulite with pure CO₂ fluid inclusions from the Fuyun region of the late Paleozoic Altay orogenic belt in Central Asia, NW China. The rock is characterized by an assemblage of garnet, orthopyroxene spinel, cordierite, biotite, plagioclase and quartz. Symplectites of orthopyroxene and spinel, and orthopyroxene and cordierite indicate decompression under UHT conditions. Mineral chemistry shows that the orthopyroxenes have high X_Mg and Al₂O₃ contents (up to 9.23 wt%). Biotites are enriched in TiO₂ and X_Mg and are stable under granulite facies conditions. The garnet and quartz from the rock carry monophase fluid inclusions which show peak melting temperatures of around-56.7°C, indicating a pure CO₂ species being presented during the ultrahigh-T metamorphism in the Altay orogenic belt. The inclusions homogenize into a liquid phase at temperatures around 15.3–23.8°C translating into CO₂ of the order of 0.86–0.88 g/cm³. Based on preliminary minerals paragenesis, reaction textures and petrogenetic grid considerations, we infer that the rock was subjected to UHT conditions. The CO₂-rich fluids were trapped during exhumation along a clockwise P-T path following isothermal decompression under UHT conditions. Project supported by the National Basic Research Program (973) of China (No. 2001CB409801), the Exemplary Young Teacher Education and Scientific Research Award Plan of China University, and Postdoctoral Fund of China (No. 2003033033), Postdoctoral Fund of Zhejiang Province, and Starting Fund of Education Ministry, China