幔源CO_(2)对中非裂谷系油气成藏的影响:以Palogue油田为例  

Effect of Mantle-Derived CO_(2) on Hydrocarbon Accumulation in Central African Rift System:A Case Study of Palogue Oilfield

作　　者：李威 窦立荣[2,3] 文志刚[3] 程顶胜 Li Wei;Dou Lirong;Wen Zhigang;Cheng Dingsheng(CNOOC Research Institute Co.Ltd.,Beijing 100028,China;PetroChina Research Institute of Petroleum Exploration and Development,Beijing 100083,China;College of Resources and Environment,Key Laboratory of Exploration Technologies for Oil and Gas Resources of the Ministry of Education,Yangtze University,Wuhan 430100,China)

机构地区：[1]中海油研究总院有限责任公司,北京100028 [2]中国石油勘探开发研究院,北京100083 [3]长江大学资源与环境学院,长江大学油气资源与勘探技术教育部重点实验室,湖北武汉430100

出　　处：《地球科学》2024年第10期3488-3498,共11页Earth Science

基　　金：国家油气重大专项项目(No.2011ZX05029);中国石油天然气股份有限公司科技专项(Nos.2013D-0902,2015D-0909)。

摘　　要：Melut盆地Palogue油田的发现打开了中非裂谷系古近系勘探新方向,证实了Melut盆地北部凹陷为富油气凹陷.Palogue油田以下白垩统为主力烃源岩,古近系为主力油藏的成藏组合,幔源CO_(2)气体对油气的聚集和改造具有不可忽略的作用.通过对CO_(2)气体、原油特征、包裹体特征进行研究,结合构造和烃源岩演化,分析CO_(2)气体与Palogue油气成藏之间的关系.结果表明:古近纪末-新近纪发生的幔源CO_(2)运移热事件对Palogue油田油气充注成藏具有重要影响.在构造-热事件作用下,烃源岩热演化迅速进入成熟阶段,发生强烈的生排烃作用,生成大量原油并融入超临界CO_(2)中,饱含原油的超临界CO_(2)快速穿层运移,发育大量高温混合烃类包裹体,即表现为异常高热事件下的快速成藏事件;饱含超临界CO_(2)的原油进入Palogue圈闭后,因地层温压条件的变化,CO_(2)气体开始向上逐层从原油中析出,携带轻质组分融入上层油藏中发生混合作用,由此导致垂向上原油物性发生一系列变化.The discovery of Palogue oilfield in Melut Basin has opened a new exploration direction of the Central African Rift Paleogene and confirmed that the northern sag of Melut Basin is rich in oil and gas resources.The Lower Cretaceous source rock is the major source rock of Melut basin,the Palaeogene is its main seal‐reservoir assemblage.The formation mechanism and model of oil and gas accumulated were proposed based on the specific tectonic-stratigraphic assemblages and evolution history of the Melut Basin.Oil and gas accumulations were influenced of mantle CO_(2).Relationship between CO_(2)and hydrocarbon accumulation was investigated using a suite of hydrocarbon generation and expulsion history,tectonic evolution history,fluid inclusions,CO_(2)and crude by taking Palogue oil reservoir as an example.The results show that the Late Paleogene-Neogene,the occurrence of the mantle source CO_(2)migration tectonic thermal event have an important influence on oil and gas accumulation in Palogue oilfield.Under the action of tectonic-thermal events,the thermal evolution of source rocks rapidly enters the mature stage,and intense hydrocarbon generation and expulsion occurs,CO_(2)in supercritical state quickly blends into crude oil.The crude oil saturated with supercritical CO_(2)quickly migrated through the reservoir and developed a large number of high-temperature mixed hydrocarbon inclusions,which showed the rapid accumulation event under the abnormal high heat event.After the crude oil full of supercritical CO_(2)entered the Palogue trap,CO_(2)gas began to separate out from the crude oil layer by layer due to the change of formation temperature and pressure conditions,CO_(2)gas carries light components into the upper reservoir for mixing.This results in a series of changes in vertical physical properties.

关 键 词：Melut盆地 PALOGUE油田 成藏过程 蒸发分馏作用 石油地质学 

分 类 号：P618[天文地球—矿床学]