摘要
氦气作为一种稀有战略资源,关系国家安全和高新技术产业发展。在总结前人成果的基础上,对柴达木盆地北缘地区各气田的氦气含量及同位素进行了分析,试图探讨常规天然气藏中的氦气成藏条件。结果表明:东坪气田的氦气含量介于0.012%~1.07%之间,平均为0.24%。利用壳—幔二元混合模式计算天然气中幔源氦的贡献比例,发现幔源氦的比例介于0.01%~0.84%之间,平均为0.3%;R/Ra值介于0.0035~0.0592之间,平均为0.0226,属于典型的壳源氦。研究区氦气含量与甲烷含量呈明显负相关,与氮气含量呈正相关关系。异常高温扰动有利于促进研究区基岩中氦气发生初次运移,马北气田与牛东气田氦气富集离不开地层水作为有效载体,而东坪气田氦气富集的载体需进一步研究。壳源成因的氦可能主要来源于基底富U、Th的花岗岩和片麻岩的放射性衰变,载氦流体运移通道主要是山前深大断裂和不整合面,盖层分为基岩上覆的含膏泥岩和泥岩的区域盖层,以及咸水下渗形成的基岩顶封式局部盖层2种,这些有利的成藏条件为研究区氦气富集提供了良好的地质基础。体积法得出研究区氦气资源量约为27×10^(8) m^(3),每克岩石平均每年产生^(4)He量约为(12.61~121.95)×10^(-20)m^(3),平均为48.81×10^(-20)m^(3)。
Helium is a kind of rare resource,which is related to national security and the development of hightech industries.Based on summarizing the previous achievements and the analysis of helium content and isotopes of various gas fields in the northern margin of Qaidam Basin,the paper tries to explore the helium accumulation conditions in conventional natural gas reservoirs.The results showed that the helium content in Dongping Gas Field ranges from 0.012%to 1.07%,with an average of 0.24%.The contribution ratio of mantle helium in natural gas is calculated by using the crust-mantle binary mixing model.It is found that the contribution ratio of mantle helium is between 0.01%and 0.84%,with an average of 0.3%;the R/Ra value is between 0.0035 and 0.0592,with an average of 0.0226,showing a crust-derived helium.The helium content in this area is negatively correlated with the CH_(4) content and positively correlated with the N_(2) content.The internal relationship between the two needs further study.Abnormal high temperature disturbance is the key to the primary migration of helium in bedrock in this area.Formation water is an effective carrier for helium enrichment in Mabei Gas Field and Niudong Gas Field,and the carrier for helium enrichment in Dongping Gas Field needs further research.The crust-derived helium was sourced from the granite and gneiss with rich uranium and thorium on the basin basement.The deep faults of the northern Qaidam Basin and the unconformity have provided good conditions for the migration of helium-bearing fluid.There are two types of caprocks,one of which is the anhydritebearing mudstone cover and mudstone cover above the basement,and the other is a top-sealed partial cover which is mainly formed by salty water seepage.These favorable reservoir forming conditions provide a good geological basis for helium enrichment in this area.According to the volume method,the helium resource in this area is about 27×10^(8) m^(3),and the average of ^(4)He content produced by per gram of rock for every year is about from(12.61~121.95)×10^(-20)m^(3),with an average of 48.81×10^(-20) m^(3)。
作者
马明
范桥辉
MA Ming;FAN Qiaohui(Northwest Institute of Eco-Environment and Resources,Chinese Academy of Sciences,Lanzhou 730000,China;Key Laboratory of Petroleum Resources,Gansu Province,Lanzhou 730000,China;National Engineering Research Center of Offshore Oil and Gas Exploration,Beijing 100028,China)
出处
《天然气地球科学》
CAS
CSCD
北大核心
2023年第4期587-600,共14页
Natural Gas Geoscience
基金
中国科学院稳定支持基础研究领域青年团队计划“氦气成藏机理与分布规律及低成本氦气富集与精制”(编号:YSBR-017)
国家自然科学基金(编号:42202193)
甘肃省自然科学基金(编号:22JR5RA080)联合资助.
关键词
氦气
成因
游离气
水溶气
成藏条件
柴达木盆地
Helium
Derivation
Free gas
Water-soluble gas
Accumulation conditions
Qaidam Basin
