松辽盆地长岭断陷东部大中型火山岩(油)气田形成分布特征

松辽盆地南部长岭断陷的东部已经发现了松南、达北、东英台、东岭等一批大中型构造—火山岩(油)气田,它们具有以下形成分布特征:1)分布于长岭、乾安、查干花等富油气断陷,这些断陷都发育巨厚湖相、湖沼相沙河子组—营城组优质烃源岩;2)在近烃源控凹断裂带及缓坡坡折带上,发育一批大型继承性鼻状隆起构造—火山岩复合圈闭;3)主力气藏分布于营城组上部的大套酸性火山岩优质储层中,上覆泥质岩为气藏的良好封盖层系;4)砂体与断裂、火山岩体等相互交织构成高效的油气运移汇聚系统;5)在各期次构造运动中,该区带始终具有良好的油气聚集和保存条件。下一步应继续围绕长岭断陷的控凹断裂带及缓坡坡折带,继续扩展勘探营城组继承性鼻状隆起构造—火山岩复合圈闭。 

Formation and distribution of large-medium scaled volcanite gas fields in eastern Changling Fualt Depression of the Songliao Basin

A series of large-medium volcanite(oil) gas fields have been found in the east of Changling Fault Depression in southern Songliao Basin,such as Songnan,Dabei,Dongyingtai,and Dongling gas fields.These volcanite(oil) gas fields have the following accumulation and distribution features.1) These fields are located in the hydrocarbon bearing depression,such as Changling,Qian'an,Chaganhua depressions,which have been proved by drilling to be bearing high quality source rocks of lacustrine and eulimnetic facies of Shahezi-Yingcheng Group.2) A lot of large inherited uplift structure-volcanite combined traps were developed near the fault belts controlling sags with source rocks and in the breaks of the gentle slopes.3) Major gas pools were distributed in massive acidic volcanite reservoir rocks in upper Yingcheng Group,which were covered with the upper sections of Denglouku Group and Quantou Group,as a favorable sealing layer.4) The sands and the fracture as well as volcanic rocks were interlaced to form complicated grid-and blanket-like hydrocarbon migration system and establish a solid foundation for large scale hydrocarbon migration and accumulation.5) In the course of late tectonic evolution since late depositional stage of Denglouku Group,the eastern part of Changling Depression have been remaining favorable accumulation and preserving conditions.Next-step work should focus on the sag-controlling fault belts and breaks of the gentle slopes in Changling Depression,exploring inherited nose-like uplift structure-volcanite combined traps in Yingcheng Group.