Petroleum Accumulation Period Of Hydrocarbon Inclusion Of Cambrian-Ordovician System In The Eastern Tarim Basin

Located in the east of the Tarim Basin,the eastern Tarim Basin is a key area for oil and gas exploration.The study is mainly concentrating on stratification of the Cambrian-Ordovician carbonate reservoirs in the area,core analysis and thin-section observations can clarify the characteristics of diagenesis.accumulate in strati-graphic minerals and veins.The Uniform temperature and salinity of the hydrocarbon inclusions and accompanying brine inclusions were tested to analysis the history and the stage of the oil and gas accumulation.Due to the overall uplift of the eastern Tarim Basin in the late Hercynian period,there was no accumulation of hydrocarbon inclusions.Five major stages of hydrocarbon inclusions were developed in the two major structural periods :two found in the Late Caledonian-Early Hercynian period,three found in the Himalayan period.But the types of hydrocarbon inclusions are different in the west and east : the western area(Gucheng 4 well,Gucheng 6 well,Tadong 2 well and Tadong 1 well)only saw the I-1 which is the black dry asphalt,the ?-2 which is the black liquid or gas phase hydrocarbon inclusions and the ?-3 which is the black gas hydrocarbon inclusion,a total of three hydrocarbon inclusions,which are nonfluorinated hydrocarbon inclusions;the eastern area(The Luoxi 1 and Yingdong 2 wells)only saw the I-2 which is the dry bitumen and the ?-1 which is showing blue-colored,colorless or light red gas-liquid hydrocarbon inclusions,with two stages of hydrocarbon inclusions,which are fluorescent hydrocarbon inclusions.It can be seen that the filling and accumulation of oil and gas at the east and west are completely different the eastern Tarim Basin.According to the geothermal-buried history map of the sampling well,combined with the homogeneous temperature analysis of its accompanying brine inclusions,the following conclusions are drawn:(1)The homogenization temperature of the I-1 hydrocarbon inclusion in the western area was 80-90°C,which formed in Late Ordovician-Silurian,belong to the late Caledonian;uniform temperature of the ?-2 associated brine inclusions in the western region is at a range of 90-100°C.The dating result of quartz is 68 Ma,indicating that it was formed in the Cretaceous,belonging to the stage of Yanshanian;the homogeneous temperature of the inclusions of the ?-2 hydrocarbon inclusions was 120-130°C,and the quartz dating was 23 Ma,which formed in the Neogene.belonging to the Himalayan.(2)There are two stages of hydrocarbon accumulation in the Luoxi 1-Yingdong 2well in the Tadong area: the I-2 hydrocarbon inclusions formed in the Late Ordovician-Silurian,belonging to the late Caledonian;the temperature of the ?-1associated brine formation is from 98.9 to 110 °C,and the quartz dating is 45 Ma,indicating the formation is in the Paleogene,belonging to period of the Himalayan.The Cambrian-Ordovician ancient reservoir in the eastern Tarim Basin is characterized by “difference between the blocks of the east and west ”,and there are differences in accumulation.The structure of the Cambrian-Ordovician paleo-reservoir is diverse and the plates are complex.The oil quality is different in each period,the sources of the oil and gas are also different: The source rocks of the western area is originate in the Manjar depression sag;and the source of the eastern region is originate in the Yingjisu sag.