利用自生伊利石K-Ar定年分析烃类进入储集层的时间

THE K-Ar ISOTOPIC DATING OF AUTHIGENIC ILLITES AND TIMING OF HYDROCARBON FLUID EMPLACEMENT IN SANDSTONE RESERVOIR

烃类流体注入储层聚集成藏导致储层中自生矿物形成的抑制或中止,成岩矿物同位素地质年代学分析提供了成岩矿物形成的准确时间,成岩事件年代学研究可用于定量分析油气藏形成时间。砂岩储层中自生伊利石仅在流动的富钾孔隙水介质环境下才能形成,烃类流体注入储层后伊利石形成便会中止,因此,烃类流体进入储层时间不可能早于自生伊利石的形成时间。利用K-Ar同位素地质年代学方法分析塔里木盆地塔中4石炭系C_Ⅱ油藏、塔北东河塘石炭系油藏和吉拉克三叠系凝析气藏3个砂岩储层的自生伊利石形成时间,分别为246—278Ma、24.3—31.8Ma和44.3—49.2Ma,反映前者第一期成藏时间为晚二叠世,后两者的成藏时间在老第三纪。

Authigenic illites in sandstone reservoirs form in the presence of flowing K-rich pore water. The entrance of hydrocarbon fluids into sandstone reservoirs brings a halt to the illite-forming processes, and if the last-formed illite can be isolated and its age determined, the maximum age of hydrocarbon entrance can be constrained. K-Ar isotopic chronological analysis has shown that the ages of diagenetic illites in the Carboniferous sandstone reservoir of the Donghetang area and the Triassic condensate reservoir of the Jilake area are 24. 3-31. 8 Ma and 44. 3-49. 2 Ma respectively , which reflects that the former petroleum reservoir formed in the Oligocene, while the latter in the Eocene.