火山岩体盖层体系域构成与圈闭有效性——以松辽盆地长岭凹陷营城组火山岩体为例

Study on capping system of volcanic rock and trap validity-case study of volcanic rock of Yingcheng formation,Changling depression

在同一盆地中并不是所有成藏条件相似的火山岩体都能够成藏,有的因为火山岩体储集空间不发育而未能成藏,有的因为缺乏必要的盖层条件而难以成藏。以长岭凹陷营城组火山岩体成藏研究为例,系统解剖了不同构造部位所钻遇的火山岩体,分析了这些火山岩体盖层的岩性与油气成藏的关系,进而研究了盖层的体系域构成。只有低位体系域和湖扩张体系域的泥岩直接覆盖的火山岩体才能成藏,而低位体系域、湖扩张体系域和高位体系域形成的砂体所覆盖的火山岩体,因缺乏有效盖层而难以成藏。因此,在进行火山岩体储层发育预测研究的同时,还应开展火山岩体盖层体系域构成分析,进一步落实火山岩圈闭的有效性,以提高勘探的成功率。

Exploration practices demonstrated that not all the volcanic rocks which have the similar formation condition in the same basin could form an oil and gas pool,some of which are due to the poorly developed storage,and others are attributed to the lack of capping conditions.Herein,the volcanic rock of Yingcheng formation in Changling depression is taken as example to present the volcanic rock drilled in different tectonic position systematically,and analyze the relationship between the lithology of capping volcanic rocks and the petroleum accumulation,and then study the composition of the capping system.The study herein presented that only the volcanic rock being covered directly by mudstone in low water level system or lake expansion system can form the reservoir,while the volcanic rock being covered by sandstone in low water level system,lake expansion system and high water level system can not form a reservoir due to the absence of effective sealing condition.Therefore,the study on volcanic rock reservoir and its composition analysis of capping system should be implemented,so as to ascertain the validity of volcanic rock trap and enhance the exploration success.