松辽盆地含CO_2火山岩气藏的形成和分布

Formation and distribution of volcanic CO_2 gas pools in Songliao basin

松辽盆地特有的深部构造背景和裂谷演化特征,造成盆地内含CO_2火山岩气藏的形成和富集。松辽裂谷盆地中新生代火山岩浆活动发育,总体上具有多期喷发、分布广泛和储集条件良好的特点。火山活动以中心式喷发为主,主要发育中基性-酸性火山岩,发育流纹岩、凝灰岩等多种岩石类型,爆发相和溢流相2种火山岩相。中生代火山岩在盆地内分布广泛,营域组构成深层有利储层,新生代火山岩在盆地外围出露较多,而在盆内出露较少。盆地高含量的二氧化碳为无机幔源成因,由青山口期和新生代幔源岩浆脱气形成。含CO_2火山岩气藏的形成主要受深部构造背景、深大断裂和中新生代火山岩控制。已发现含CO_2火山岩气藏主要分布于古中央隆起带及其两侧断陷的营城组火山岩中,具有点状、带状分布,局部富集的特点。根据主控因素分析,预测了5个CO_2富集区带。

The unique tectonic setting and rift evolution of Songliao basin resulted in the formation and enrichment of volcanic CO_2 gas pools.Mesozoic-Cenozoic volcano-magmatic activities developed in Songliao rift basin,with characteristics of multi-phase eruption, wide distribution and good reservoir condition.Volcanic activities were generally central vent eruption,mainly developing medium-basic and acidic volcanic assemblages,rhyolite,tuff and other rock types,two types of explosive facie and effusive facie.Mesozoic volcanic rocks are widely distributed in the basin,including Upper Jurassic Huoshiling Formation,Lower Cretaceous Yingcheng Formation constituting favorable reservoir of deep level of the basin,while Cenozoic volcanic rocks more exposed outside the basin and less drilled in the basin.Highly-enriched CO_2 in the basin is of mantle-derived inorganic origin caused by mantle-derived magma degassing during Qingshankou and Cenozoic volcanic activity period.The formation of volcanic CO_2 gas pools are mainly controlled by the background of deep structure,deep-large faults and Mesozoic-Cenozoic volcanic rocks.Discovered volcanic CO_2 gas pools are mostly distributed in volcanic rocks of Yingcheng Formation in ancient central uplift and its adjacent faulted depression,characterized with point-belt distribution and local enrichment.Based on the controlling factor analysis,five CO_2 accumulation plays were predicted.