天然气藏He的累积模式及定年应用初探

Helium Accumulation Mode in Natural Gas Reservoirs and Its Application in Dating

天然气藏He的聚集存在一定的年代累积效应,借鉴相关地质模型,引入气藏特征参数,对外部壳源以及气藏原位产生的He进行量化,明确天然气藏中He累积量与时间的数学关系,进而建立了约束天然气藏形成时代的新方法——He定年模型。将该方法应用于四川盆地威远气田,估算威远震旦系天然气成藏定型的时间约为31Ma,对应渐新世,处于喜马拉雅运动中期。该结果与威远气田成藏过程的研究成果相吻合,表明天然气藏He的年代累积效应可以用于成藏时代的研究,所建立的He定年模型具有一定的实用性和应用潜力。

Helium accumulation in gas reservoirs has some accumulative effect for age. Based on the relevant geological model and introduction of gas reservoir parameters, this study conducted quantitative analysis for radiogenic He from crust flux and gas reservoir so as to establish a mathematic relation between He accumulation in gas reservoir and time, and finally establish a new method-He dating method, which can constrain the formation time of natural gas reservoirs. This method was applied in the Weiyuan gas field of Sichuan Basin. It is estimated that the natural gas reservoirs in Weiyuan formed at 31 Ma, which is corresponding to Oligocene and around the mid-Himalayan movement. The age is consistent with result of gas formation and accumulation history,indicating the model of He accumulation can be used to study the formation time of gas reservoir.