长岭凹陷深层天然气藏中CO_2及CH_4充注次序的流体包裹体证据

The fluid inclusion evidence for the charging sequence of CO_2 and CH_4 in the natural gases reservoir in deeper level parts of Changling depression

对长岭凹陷深层天然气藏储层——营城组火山岩中发育的流体包裹体进行了详细研究,结果表明在火山岩发育的石英、方解石细网脉中均存在较多的碳质流体包裹体,单个包裹体激光拉曼光谱分析结果表明其主要为CO2及CH4两种类型的碳质包裹体。其中方解石细网脉体中发育有原生及次生CH4包裹体,而含CO2包裹体多以原生包裹体产于石英细网脉中。很多含CO2包裹体的石英细脉中发现了含CH4包裹体的方解石脉体的角砾,这就表明石英细脉形成晚于方解石细脉。营城组火山岩储层中CO2及CH4包裹体的产状特征研究表明,松辽盆地深层天然气藏的形成系火山岩成岩后CO2及CH4等气体不同期次充注的结果,CH4气的充注时间早于CO2气,火山岩中发育的原生孔隙及次生裂隙为上述气体的充注和聚集提供了重要通道。

Careful fluid inclusion study were carried out on Yingcheng Formation of volcanic rocks,an important deep seated natural gas reservoir strata in Changling depression,the results showed that there are abundant carbonic fluid inclusions existed in quartz and calcite veinlets developed in this set of volcanic rocks,there are mainly CH4 and CO2two types were identified by laser Raman microprobe analysis on compositions of single fluid inclusions. Primary as well as secondary CH4 fluid inclusions mainly occurred in veinlet calcite,while CO2 inclusions,however,only found in quartz veinlets and occurred mainly as randomly distributed primary inclusions. In some veinlet quartz,calcite breccias that containing CH4 inclusions have been found,that indicates quartz veins formed later than calcite veins. Based on study of petrological as well as compositional features of carbonic fluid inclusions developed in Yingcheng Formation of volcanic reservoir rocks,we obtained some preliminary conclusions： the deep seated natural gas fields in Songliao basin were the results of asynchronous charging of CH4 and CO2gases,the infilling of CH4 predated that of CO2 and primary holes / porosities as well as secondary cracks developed in volcanic rocks served as the main route ways for the charging and accumulating of CH4 and CO2,etc. gases.