松辽盆地长岭断陷火山岩天然气藏分布规律与控制因素

Distribution patterns and controlling factors of volcanic gas pools in the Changling fault depression,the Songliao Basin

在长岭断陷火成岩天然气成藏条件以及各成藏要素时空配置关系综合分析的基础上,讨论了天然气富集规律及主控因素。研究表明,长岭断陷烃类气藏主要分布在凹陷中部低凸起带腰英台、达尔罕构造及东部斜坡带双龙构造,其中营城组爆发相凝灰岩和溢流相流纹岩为最有利的储集层。控制天然气富集的因素主要包括:①断陷层深部烃源岩的分布范围宏观上控制油气分布;②火山岩体及其有利的储集相带控制气藏的形成与分布;③深大断裂是油气形成的重要条件;④良好的盖层和侧向遮挡条件决定了纵向上油气的分布;⑤在基底断裂沟通良好的前提下,早期充注的烃类与晚期CO2形成有机-无机混源气藏;⑥大型继承性古隆起(古斜坡)、地层超覆尖灭、火山岩体形成的复合圈闭是最有利目标区。

Based on a comprehensive analysis of gas accumulation conditions and temporal-spatial combinations of accumulation elements,in this paper we make a study of enrichment pattern and main controlling factors of volcanic gas reservoirs in the Changling fault depression.The results show that gas pools are mainly distributed in the Yaoyingtai and Da＇erhan structures in the low salient of central sag and the Shuanglong structure in the eastern slope belt.Volcanic tuff of explosive phase and rhyolite of overflow phase in the Yingcheng Formation are the most favorable reservoirs.The major controlling factors for gas accumulations are as follows：1）distribution of deep source rocks controls the oil and gas distribution in a macro way;2）volcanic rocks and their favorable reservoir facies control the development and distribution of gas pools;3）discordogenic faults are important conditions for the development of oil/gas pools;4）quality cap rocks and lateral seals determine the vertical distribution of gas;5）the early charged hydrocarbons get mixed with later-generated CO2 when basement faults have good conductivity,leading to the formation of mixed gas pools with both organic and inorganic origins;6）favorable targets are compound traps formed by large-scale inherent palaeohighs（palaeoslope）,onlapping pinchouts and volcanic rocks.