主成盆期火山岩与油气成藏关系探讨

Relationship between Volcanic Rocks and Hydrocarbon Accumulation during Dominant Period of Basin Formation in Liaohe Depression

裂陷盆地的主成盆期是构造活动性最强、沉降幅度最大、烃源岩发育最好的时期,辽河坳陷的主成盆期是E2s4～E2s3时期。辽河坳陷新生代发生了多期火山活动,形成了多套、多类型的火山岩分布,火山活动总体上具有早强晚弱、平面上具有随沉降中心变迁而迁移的活动规律。辽河坳陷主成盆期火山岩经过构造裂缝作用及地层水溶蚀、溶解改造后,发育为良好的油气储层,有效烃源岩与穿插其中的火山岩在平面上的叠覆和剖面上的交互为形成火山岩油气藏提供了充沛的油气源供给条件。同时,主成盆期火山岩厚度大、分布广,圈闭及成藏类型多样,具有多方面的油气成藏有利性,黄沙坨及欧利坨子等地区的火山岩油气藏是其中的典型代表。主成盆期火山岩具有有利的油气成藏组合,而非主成盆期火山岩一般作为油气藏盖层。主成盆期火山岩成藏及其模式的提出丰富了火山岩油气成藏内容及油气勘探类型,对其他地区火山岩勘探也具有重要的指导意义。

The dominant period of basin formation is defined as the period with the strongest tectonic movements,the largest extent of subsidence and the best development of source rocks.The sedimentary period of the 3rd member（Shasan,E2s3） and 4th member（Shasi,E2s4） of Shahejie Formation is the dominant period for basin formation.There were many episodes of volcanic movements during Cenozoic in Liaohe Depression,forming distribution of volcanic rocks with many series and types,which changes with the tectonic center and has the less strong activity in the earlier stages.The volcanic movements in the dominant period of Liaohe depression are abnormally strong and the appearances of volcanic rocks are frequent.The reservoirs which are altered by structural fractures and the corrosion and dissolution by formation water are favorable for oil and gas accumulation.The superposition in plane and the alternation in profile provide enough provision conditions of oil and gas sources for volcanic rock reservoirs.Furthermore,the volcanic rocks from dominant period of basin are of large thickness,widespread distribution and various traps and accumulation types,owning many advantages for oil and/or gas accumulation in many respects.The volcanic rock reservoirs for oil and/or gas in the areas of Huangshatuo and Oulituozi are typical representations among the above favorable reservoirs.The volcanic rocks from the dominant period of basin formation with favorable combination of oil and/or gas accumulation,enriching the content of oil and /or gas accumulation and the types of oil and /or gas exploration,are the important field for hydrocarbon discovery and exploration.