塔中地区奥陶系储层烃包裹体特征及成藏分析

Characteristic of hydrocarbon fluid inclusions and analysis of reservoir formation in Ordovician reservoir of Tazhong area,Tarim basin

利用新发明的不同期次烃包裹体组份提取仪器"多功能烃包裹体取样机",分别提取了塔中地区5期烃包裹体组份,并成功地分析出组份生物标志化合物,论证了5期烃包裹体油气的来源:第Ⅰ期烃包裹体来源于满加尔坳陷的寒武系海相碳酸盐岩烃源岩、第Ⅱ期烃包裹体来源于满加尔凹陷的中奥陶系烃源岩、第Ⅲ期烃包裹体来源于塔中下部寒武系海相碳酸盐岩烃源岩、第Ⅳ期烃包裹体是由寒武系海相碳酸盐岩原油分解而成、第Ⅴ期烃包裹体来源于塔中上奥陶统良里塔格组烃源岩。其形成时间分别为:早海西期约383Ma、晚海西期约240～260Ma、燕山-早喜山期早期、23Ma喜山运动二幕、喜山运动晚期到现在。塔中奥陶系储层中不是每一个圈闭都含有以上5期烃包裹体,有的圈闭只含其中的一期或二期或三期。第Ⅰ期主要是油气运移的"足迹",仅路过奥陶系,未成藏。第II、IV、V期成藏普遍影响塔中奥陶系,是油气成藏的"历史",使奥陶系的原油具有中奥陶统油源(第II期)、上奥陶统油源(第V期)和寒武系油源(第IV期)混源特征,第Ⅱ、Ⅳ期烃包裹体大量存在是塔中Ⅰ号坡折带凝析油气高产的"标志"。第Ⅲ期包裹体的发育可能预示在塔中东部地区中下奥陶统及寒武系形成大油藏,塔中东部地区是找原生大型油藏的重要靶区。

Hydrocarbon inclusions in Ordovician reservoirs of Tazhong area can be divided into five periods.Component of these inclusions which have significant contribution to reservoir formation have been extracted by using the new invented extraction equipment ＇multi-functional hydrocarbon inclusions sampling machine＇,and the oil and gas sources of these five periods of hydrocarbon inclusions have be studied in this paper.The oil in hydrocarbon inclusions of period Ⅰ derived from the Cambrian marine carbonate source rocks in Manjiaer depression,that of period II from the Ordovician source rocks in Manjiaer depression,that of period Ⅲ from the Cambrian marine carbonate source rocks in Tazhong area,that of period Ⅳ from the decomposition of crude oil which derived from Cambrian marine carbonate source rock,and that of of period Ⅴ from Lianglitage Formation of Upper Ordovician source rocks in Tazhong area.The formation time of these five periods of hydrocarbon inclusions were Early Hercynian about 383Ma,Late Hercynian about 240~260Ma,Yanshan-Early stage of Early Himalayan,the second episode of Himalayan movement at 23Ma,the Late Himalayan to the present respectively.Distribution of respective five periods of hydrocarbon inclusions varied from trap to trap of Ordovician reservoir in Tazhong,some traps contained only one or two or three periods of hydrocarbon inclusions.Oils of period Ⅰwas the ＇footprint＇ of hydrocarbon migration,just passing through the Ordovician,did not accumulate.Oils of periods II,IV,V were the ＇history＇ of oil and gas accumulations.The Ordovician oil has the mixed-source characteristics of oil from Middle Ordovician source rock（period II）,oil from upper Ordovician source rock（period V）and oil from Cambrian source rock（period IV）.Abundance of hydrocarbon inclusions of periods Ⅱ,Ⅳ were the ＇sign＇ of productive condensate oil and gas in Tazhong No.I slope break belt.Accumulation of period Ⅲ may form large reservoirs in Lower Ordovician and Cambrian in the eastern region of Tazhong area,so the eastern region is an important target zone to explore for large primary reservoirs.