库车前陆盆地迪那2气田成藏机理及成藏年代

Reservoiring mechanism and finalization period of Dina 2 gasfield in Kuqa basin

孙冬胜 金之钧 吕修祥 周新源 杨明慧

Sun Dongsheng Jin Zhijun Lu Xiuxiang Zhou Xinyuan Yang Minghui

库车前陆盆地具有典型的双超压体系。深部超压体系的形成过程与源岩快速大量的生气作用密切有关,同时也决定了中生界源岩生成的天然气主要以水溶气形式存在。上部超压体系具有常压成藏的特点,当深部超压体系中的天然气沿断裂以混相涌流方式进入上部常压环境后,发生脱气析出并聚集成藏,其后,经构造运动进一步的挤压作用形成上部超压体系。迪那2气田是上部超压体系中的天然气成藏。在圈闭发育史及源岩生烃史分析的基础上,结合储层流体包裹体及自生矿物伊利石的K/Ar测年数据,认为迪那2气田发生过3期油气的充注,古近纪末期为液态烃注入,但遭受破坏;库车早中期为气液两相注入;库车晚期及西域早期为天然气注入,第三期是成藏的关键时期。

There are two overpressure systems,lower and upper overpressure systems,in Kuqa foreland basin.The former was closely related with rapid and large gas generation,and thus the gas generated from Mesozoic source rocks mainly took the form of water-soluble gas.The upper overpressure system has the characteristics of reservoiring at normal pressure.When gas in the lower overpressure system migrated upward along faults in the form of miscible fluids into the upper normal pressure environment,degasification would occur and then accumulated in reservoirs.At a later stage,the upper overpressure system was formed under further compression of tectonic movement.Dina 2 gasfield is the final results of gas accumulation in the upper overpressure system.Based on analysis of trap development history and hydrocarbon generation history,in combination with fluid inclusion in the reservoir and K/Ar dating of authigenic illite,it is believed that Dina 2 gasfield had been charged in three different stages.In the first stage,liquid hydrocarbons were charged at the end of Paleogene and destroyed later.In the second stage,mixed liquid and gaseous hydrocarbons were charged in early-middle Kuqa stage.In the third stage,natural gas was charged in late Kuqa and early Xiyu stages,which was the key reservoiring stage of the field.

10.11743/ogg20040516