松辽盆地火山岩包裹体稀有气体同位素与天然气成因成藏示踪

长期以来,国内外油气勘探主要是针对海相碳酸盐岩和海陆相碎屑岩,火山岩原来一直是油气勘探的禁区。松辽陆内裂谷盆地燕山期由于太平洋板块对中国大陆板块的斜向俯冲,发生弧后伸展裂陷,造成火山岩的大量喷发,以爆发相和溢流相为主。火山岩储层物性较好,不严格受埋深控制,但非均质性强,孔隙度0.5%~18.7%不等,渗透率0.0001×10^-3~1×10^-3μm²。火山岩裂缝内方解石脉或石英脉中包裹体捕获温度为105~250℃,多数在120~160℃;包裹体中气体³He/⁴He值分布在2.86×10^-7~7.33×10^-6,平均为2.48×10^-6;R/Ra＝0.26~5.24,多数R/Ra>1; ⁴⁰Ar/³⁶Ar＝293~2485,主值区间为500~900;⁴He/²⁰Ne＝0.32~1255,主值区间为10~95和170~370;δ¹³C₁=-17.1‰~-28.7‰,δ¹³C₂=-23.4‰~-32.4‰,δ¹³Cco₂=-10.97‰~-21.73‰。包裹体He、Ar、C等同位素数据表明,存在幔源通道,进而在火山岩中存在幔源无机成因气。根据火山岩产状和分布及其与断裂活动的关系,无机成因气藏主要分布于断裂带附近,有机成因气或有机-无机混源气则远离断裂活动带分布。本文包裹体同位素研究结果对确定松辽盆地深层火山岩储层中的天然气成因类型、分布规律,指导后续天然气勘探具有重要的参考价值。

The trace of genesis, formation and mineral resources of natural gas and rare gas isotope existing in volcanic inclusion of Songliao basin.

Ever since a long time ago,the oil-gas exploration home and aboard is mainly about marine facies carbonatite and sea and land facies clastic rock.Volcanic is always the forbidden area of exploration.In Yanshan Period,because of slant diving of pacific plate to Chinese continental plate,the rift basin in Songliao took place the back-arc stretch rift and causes the mass eruption of volcanic which is mainly eruption facies and overflowing facies.The quality of reservoir of volcanic is better and not strictly controlled by burial depth,but its anisotropy is obvious and porosity is 0.5%～18.7% and permeability is 0.0001×10-3～1×10-3μm2.The catching temperature of inclusion in calcite vein or quartz vein in crack of volcanic is 105～250℃,and majority is 120～160℃,and the 3He/4He specific value of gas in inclusion is 2.86×10-7～7.33×10-6 and the average number is 2.48×10-6.R/Ra=0.26～5.24,majority of R/Ra>1.40Ar/36Ar=293～2485 and the principle value interval is 500～900.4He/20Ne=0.32～1255,the principle value interval is 10～95 and 170～370.δ13C1=-17.1‰～-28.7‰,δ13C2=-23.4‰～-32.4‰,δ13Cco2=-10.97‰～-21.73‰.The data of He,Ar,C and other isotopes in inclusion reveal that there is mantle-genetic path,so there is mantle-genetic inorganic genetic gas in the volcanic.According to the attitude and distribution of volcanic and its relationship with rifting activity,inorganic genetic gas exists mainly around the rift vein and organic genetic gas or the mixture gas of inorganic genetic gas and organic genetic gas mainly exists far away from the rift vein.The research results of isotope in inclusion in this article have the significant reference value of confirming the genetic type and distribution of gas in the deep volcanic reservoir in Songliao basin and guiding the following exploration of natural gas.