坦桑尼亚鲁夸裂谷盆地氦气充注及成藏机理研究  

Research on helium charging and accumulation mechanism in Rukwa Rift Basin in Tanzania

作　　者：吴义平[1] 王建君[1] 陶士振[1] 王青[1] 雷占祥[1] 李谦[1] 张宁宁[1] 王晓波[1] 杨怡青 WU Yiping;WANG Jianjun;TAO Shizhen;WANG Qing;LEI Zhanxiang;LI Qian;ZHANG Ningning;WANG Xiaobo;YANG Yiqing(Research Institute of Petroleum Exploration and Development of PetroChina,Beijing 100083,China)

机构地区：[1]中国石油勘探开发研究院,北京100083

出　　处：《地学前缘》2025年第2期261-276,共16页Earth Science Frontiers

基　　金：中石油关键核心攻关技术项目(2021ZG13)。

摘　　要：氦气成藏机理具有特殊性,比油气系统更复杂。自1967年在坦桑尼亚克发现富氦温泉以来,尚未发现规模氦气田,鲁夸裂谷盆地能否形成富氦气藏值得关注。本文利用地球化学、地震、钻井、测井等资料,综合分析了该盆地生氦资源量、氦气释放过程和充注机制,进而探讨了氦气勘探潜力。研究表明:中、新生代裂谷对盆地氦气的运移和聚集具有重要控制作用;地表氦气含量为1.0%~10.2%,载体气类型为氮气、二氧化碳和甲烷,^(3)He/^(4)He值在0.039~0.053 R_(a)之间,表现为壳幔混源特征,盆地基底和沉积岩生氦量为367亿m^(3);氦气从源岩到圈闭以及地面经历了生成、释放、运移、充注和溢出5个过程。氦气充注机制主要表现为氮气氦气脱溶充注、煤层气氦气萃取充注和二氧化碳氦气萃取充注3种。其中氮气为深部成因的无机气,与氦气具有同源特征,为盆地的主要充注模式;煤层气来源于盆地沉积中心,与氦气为异源同储;二氧化碳为变质成因无机气,与氦气共生机制与煤层气相同。盆地的有利成藏区带为盆地边界断层(BMF)带。在此处的上覆土壤带,氦气含量比背景值高出35%,目前已发现12个盆地边界断层圈闭(BMFC),风险前氦气远景地质资源量为57.4亿m^(3),占盆地待发现资源量的64.6%,成为裂谷盆地的有利勘探目标。The mechanism of helium accumulation is unique and more complex than that of petroleum systems.Since the discovery of helium-rich hot springs in Tanzania in 1967,no large-scale helium fields have been identified.To establish the mechanism of helium charging and accumulation in the Rukwa Rift Basin,this study conducted research in five key areas using geochemical,seismic,drilling,and logging data:analyzing the helium and carrier gas content at the surface,calculating helium production in the craton basement,examining the helium release process,establishing the helium charging mechanism,and identifying favorable helium zones.The findings reveal that the Mesozoic-Cenozoic rifts play a critical role in controlling helium migration and accumulation within the basin.Surface helium content ranges from 1.0% to 10.2%,with carrier gases including nitrogen,carbon dioxide,and methane.The ^(3)He/^(4)He isotope ratio ranges from 0.039 to 0.053 R_(a),indicating that helium originates from both crustal and mantle sources.Helium generation in the basement and sedimentary layers is estimated at 367 billion cubic meters.The release of helium from the peripheral rift of the Tanzanian Craton involves five key processes:generation,release,migration,charging,and overflow.Three helium accumulation models have been identified in the Rukwa Basin:nitrogen-helium desorption,coalbed methane-helium extraction,and carbon dioxide-helium extraction.Nitrogen,an inorganic gas of deep origin,is characterized by accumulation from homologous sources,with helium desorption from water being the primary helium charging mechanism in the basin.Coalbed methane,primarily sourced from the depositional center of the basin,accumulates independently of helium.Carbon dioxide,an inorganic gas of metamorphic origin,shares a symbiotic accumulation mechanism with helium similar to that of coalbed methane.The most favorable helium-rich zones in the basin are located in the Basin Margin Fault Closures(BMFCs).In the overlying soil of these traps,helium content is 35% h

关 键 词：气苗 盆地边界断层圈闭 脱溶 萃取 氦源 聚集 潜力 

分 类 号：P618.130.2[天文地球—矿床学] P631.81[天文地球—地质学]