鄂尔多斯盆地东胜与大牛地气田壳源氦气成藏差异性

Research on the difference of crustal helium accumulation in Dongsheng and Daniudi gas fields,Ordos Basin

当前研究发现,氦气的成藏与天然气具有耦合效应,二者表现为异生同储关系,但氦气的成藏理论尚不完善。研究从氦源岩、运移方式等方面入手,剖析鄂尔多斯盆地东胜与大牛地气田氦气成藏差异性,研究表明:①2个气田主要氦源均为基底岩石氦气,东胜气田可能氦源岩有富U、Th的基底岩石、煤层,大牛地气田可能氦源岩有基底岩石、煤层与铝土岩层;②东胜气田内部发育连通基底的断裂,为烷烃气与氦气运移提供通道,大牛地气田下方也存在基底断裂,但气田内部靠生烃作用产生的微裂缝进行运移;③对比二者成藏模式,认为连通基底与储层的深大断裂对于氦气成藏具有促进作用。

Current studies have found that there is a coupling effect between the accumulation of helium and natural gas,and the two show an allogenetic and co-storage relationship.The differences of helium accumulation between Dongsheng and Daniudi gas fields in the Ordos Basin were analyzed from the aspects of helium source rock and migration mode.The results showed that:(1)The main helium source of the two gas fields is basement rock helium gas.The helium source rock of Dongsheng Gas Field may contain basement rock and coal seam rich in U and Th,while the helium source rock of Daniudi Gas Field may contain basement rock,coal seam and bauxite rock.(2)In Dongsheng Gas Field,faults connected with the basement are developed,providing a channel for the migration of alkane gas and helium gas.In Daniudi Gas Field,basement faults also exist,but the gas field is migrated by micro-fractures generated by hydrocarbon generation.(3)It is concluded that the deep and large fault connecting basement and reservoir plays an obvious role in the accumulation of helium gas.