鄂尔多斯盆地东胜富氦气田成藏特征及其大地构造背景

Accumulation characteristics of Dongsheng helium-rich gas field in Ordos Basin and its tectonic background

近年来,在鄂尔多斯盆地北缘东胜气田上古生界天然气中发现伴生的氦气,含量分布在0.045%~0.487%范围内,具有工业价值,其三级储量约为8.3亿立方米,为一特大型含氦—富氦天然气田。东胜气田氦气属于典型的壳源氦,来源于基底的太古界—元古界变质岩—花岗岩系,富集与燕山期以来的岩浆侵入、断裂活动有关。东胜气田具备有利的氦气成藏地质条件,伴生氦气与烃类气具有异源同储成藏特征,剖析其成藏主控因素为:基底富U、Th岩石发育是基础,断裂活动是核心,储盖圈保条件是必备,时空配置是关键,其中早白垩世是最重要的一期构造—岩浆热事件,深源岩浆活动导致的深部物质和热能的大规模上涌是中生代流体成藏(矿)的有利地球动力学背景,控制了鄂尔多斯盆地石炭系—二叠系煤系烃源岩大规模生气。断裂活动和圈闭形成与上古生界天然气、氦气聚集成藏具有良好的时空配置关系,与华北克拉通破坏过程耦合。鄂尔多斯地块在早白垩世至中新世深部热流体对盆地发生的多期岩浆活动、基底断裂活化及浅部断裂活动具有明显的控制作用,同时也对石炭系—二叠系煤系烃源岩成烃成藏具有重要的控制作用。

In recent years,commercial helium associated with natural gas has been discovered in the Upper Paleozoic in Dongsheng gas field,in the northern part of Ordos Basin,with helium content ranging from 0.045%to 0.487%.The 3 P reserves of helium gas are about 8.3×10~8 m~3,which is the first super giant helium-rich natural gas field in China.The helium in Dongsheng gas field belongs to typical crust source,which is derived from the Archaean-Proterozoic metamorphic-granite series in the basement and its enrichment is related to magmatic intrusion and fault activity since the Yanshan Orogeny.Dongsheng gas field has favorable geological conditions for helium accumulation,with helium and natural gas from dif ferent sources but accumulated in the same reservoir.The main controlling factors of helium accumulation including the development of U-and Th-rich rocks in the basement,fault activity,good combination of reservoir,cap,trap and preservation,and the temporal-spatial configuration.The most important tecto nic-magmatic-thermal event occurred in the Early Cretaceous,and the large-scale upwelling of deep material and heat energy caused by deep magmatic activity was the favorable geodynamic background for the Mesozoic fluid accumulation(mineralization),which controlled the large-scale gas generation of the Carboniferous-Permian coal source rocks in the Ordos Basin.Coupled with the destruction process of the North China Craton,the fault activity and trap formation had a good spatial and temporal relationship with the accumulation of hydrocarbon gas and helium of the Upper Paleozoic.From the early Cretaceous to Miocene,the deep thermal fluid in the Ordos block significantly affected the multiple-period magmatic activity,basement fault reactivation and shallow fault activity,as well as controlled the hydrocarbon generation and accumulation of the Carboniferous-Permian coal type source rocks.