松辽盆地火山岩储层天然气藏He同位素组成累积效应  

Accumulative Effect of Helium Isotope in Gas Volcanic Reservoirs in Songliao Basin

作　　者：杨春[1] 陶士振[1] 侯连华[1] 米敬奎[1] 杨帆[1] 

机构地区：[1]中国石油勘探开发研究院,北京100083

出　　处：《天然气地球科学》2014年第1期109-115,共7页Natural Gas Geoscience

基　　金：国家科技重大专项(编号:2011ZX05001-003)资助

摘　　要：地质演化过程中,天然气藏储层中放射性元素衰变产生的3 He和4 He会在气藏中逐渐积累,使气藏中He同位素组成(3 He/4 He)产生变化。以松辽盆地徐家围子断陷和长岭断陷深层火山岩储层天然气藏为研究对象,对火山岩储层天然气和储层流体包裹体中的He同位素进行研究。当火山岩储层无Li元素含量异常时,放射成因3 He产率很低,基本可以忽略,放射性元素衰变产生的3 He不会影响CH4/3 He值和CO2/3 He值2项地球化学指标。当火山岩储层中放射性元素丰度高于沉积岩层中时,在地质历史中会产生更多的4 He,对气藏中He同位素的影响较大。营城组火山岩每克岩石每年生成4 He约为5.1×10-12cm3。在不考虑扩散的情况下,Xs1-1井营城组火山岩初始的3 He/4 He值为3.51×10-6,即R/Ra值为2.51,现今R/Ra值为1.1,当R/Ra值减小到初始值的43.8%时,幔源He的比例相应从原来29.9%减少到目前的10.75%,即幔源He的比例减小到原始的1/3。In natural gas reservoir,a He and ~ He are produced and accumulated by radioactive elements decay and resulted in the changing of a He/4 He during geological time. In this paper,we discuss the volcanic gas reservoirs in the Xujiaweizi and Changling fault depressions of Songliao Basin because the high ratio of helium isotope in the gas reservoirs. It is negligible for a He produced at a very low level due to no Li concentra- tion abnormity in this area. So, the elements decay does not affect the two ratios of CH4/aHe and CO2/a He. The volcanic rocks contain more radioactive elements than that of sedimentary rocks, and the for- mer will produce more 4 He to influence the Helium isotope in gas reservoirs. In volcanic rock reservoirs of the Xujiaweizi and Chagnling fault depressions, lg volcanic rock in the Yingcheng Formation can produce 5.1×10-12 cma4He per day. In the volcanic rocks of Yingcheng Formation at Xujiaweizi,primary ratio of aHe/4He was 3.51 × 10-6 ,and the corresponding R/Ra was 2.51. But it is 1.10 at present. R/Ra dimin- ished to 43.8% of the primary value and the proportion of mantle helium reduced from 29.9% to 10.95%, which is to say that the mantle gas decreased to 1/3 of the primary one.

关 键 词：HE同位素 放射成因He 累积效应 火山岩 松辽盆地 

分 类 号：TE122.113[石油与天然气工程—油气勘探]