我国富氦盆地成藏模式对煤系氦气富集和勘探的启示

Implications of helium accumulation models in helium-rich basins in China for the enrichment and exploration of helium in coal measures

  • 摘要:
    背景 氦气是我国紧缺的战略性资源,加强其勘查对保障国家资源安全至关重要。我国煤系气资源丰富且伴生氦气成藏潜力显著,但相关研究尚处起步阶段。
    方法 基于天然气藏氦气生成−运移−成藏理论总结和分析,系统揭示煤系氦气富集规律并提出勘探方向。
    结果和结论 获得以下认识:(1) 我国氦气资源呈现“南北分区、东西分带”的分布格局,可以分为东部幔源富氦区、中部壳源富氦区和西部壳−幔混合富氦区,其空间分异受控于盆地构造类型与区域演化背景;(2) 氦气成藏遵循源岩析出−跨层运移−圈闭聚集的动态过程,受氦源封闭性、运移通道有效性(断裂系统与微孔毛细管作用)、流体动力场及储盖配置的复合控制,其中圈闭条件为主导因素,垂向运移以断裂系统为核心,岩性储盖组合提供辅助封存,溶解−析出机制形成局部富集补充;(3) 含煤盆地氦气生成时效显著长于煤系烃类,但成藏高峰期呈现时空耦合特征,煤系兼具自生自储双氦源属性,与天然气藏构成多层立体叠置关系;(4) 煤系氦气具有多源混合、广域伴生、立体富集及低浓度特性,其成藏机制涉及多源供氦贡献度、跨系统扩散动力学、构造控藏效应及低丰度资源评价等关键科学问题,未来勘查应聚焦构造活动带微构造系统、煤系多类型储层、深部储集层及盆地边缘气藏;(5) 煤系氦气应坚持“以量补质”思路,优先在鄂尔多斯盆地、黔西滇东等代表性潜力区开展风险勘探,构建“靶区优选−煤系多储层协同开发”与“勘查−开发−利用”全链条技术体系,集成氦气提纯技术与“氦−煤−气”多资源协同开发模式,实现煤系氦气资源高效动用。研究成果为煤系氦气勘探提供理论参考和技术路径,助力国家氦气资源安全保障目标实现。

     

    Abstract:
    Background Helium is a strategic resource in serious short supply in China, and intensifying its exploration is crucial to national resource security. China enjoys abundant coal measure gas and significant potential for associated helium accumulation. However, relevant research remains in its infancy.
    Methods Based on a summary and analysis of helium generation, migration, and accumulation theories in natural gas reservoirs, this study systematically investigated the enrichment patterns of helium in coal measures and proposed exploration targets.
    Results and Conclusions  The insights reveal that the helium resources in China exhibit a distribution pattern of zoning in both north-south and east-west directions. Specifically, helium-rich basins in China are distributed in three regions: the eastern mantle-derived helium-rich region, the central crust-derived helium-rich region, and the western region rich in helium from a crust-mantle mixing source. The spatial differentiation of these helium resources is governed by both the structural types of basins and regional evolutionary background. Helium accumulation follows a dynamic process consisting of helium exsolution from source rocks, cross-strata migration, and accumulation in traps. This process is jointly controlled by the sealing performance of helium sources, the effectiveness of migration pathways (fault systems and the capillary pressure of micropores), hydrodynamic fields, and reservoir-cap rock configuration. Among these factors, traps serve as a dominant factor in helium accumulation, helium vertical migration primarily occurs through fault systems, lithological reservoir-cap rock configuration provides auxiliary helium sealing, and the dissolution-exsolution mechanism facilitates local helium enrichment as a supplement. In coal-bearing basins, helium exhibits a prolonged generation period compared to coal-seam hydrocarbons. However, the spatiotemporal coupling of helium and hydrocarbons can be observed during peak helium accumulation. Coal measures serve as dual helium sources (i.e., self-generation endogenous and self-storage exogenous helium), forming multi-layer stacked helium-bearing systems by combining natural gas reservoirs. Helium in coal measure is characterized by multi-source mixing, widespread association with other gases, three-dimensional enrichment, and low concentration. Therefore, its accumulation mechanisms involve multiple critical scientific issues including the contributive degrees of multiple sources, cross-system diffusion dynamics, the accumulation-controlling effect of structures, and the evaluation of low-abundance resources. Future exploration should focus on microstructural systems in tectonically active zones, multiple types of coal measure reservoirs, deep reservoirs, and basin-margin gas reservoirs. It is recommended to conduct the exploration and production of helium in coal measures following the philosophy of “compensating quality with quantity”. Specifically, the risk exploration of helium in coal measures in representative potential regions such as the Ordos Basin, western Guizhou, and eastern Yunnan should be prioritized; it is necessary to develop a comprehensive technical system that incorporates the selection of the optimization target areas and the commingled production of multiple coal measure reservoirs and involves the entire chain covering exploration, development, and utilization, and it is advisable to integrate helium purification technologies and the “helium-coal-gas” collaborative development model. All these will help achieve the efficient production of helium in coal measures. The result of this study will offer a theoretical reference and technical pathway for the exploration of helium in coal measures, thereby contributing to the national helium resource security.

     

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