【摘要】 为了确定柴达木盆地勘探新层系,测试并分析了该盆地5个油气田的8个天然气样品的氦、氩同位素比值,探讨了其在大地构造背景、大地热流和气源方面的示踪意义。研究结果如下:①柴达木盆地8个天然气样品3He/4He值分布在2.0×10-8~5.48×10-8的范围,总体平均为3.7×10-8,均在10-8量级,体现了典型的壳源成因氦同位素的特征。②据3He/4He计算的大地热流值较低,分布于41.2~48.2 mW/m2之间,平均44.9 mW/m2,低于东部地区大地热流平均值73 mW/m2,表明该盆地具有较稳定的构造背景。③根据天然气40Ar/36Ar的年代积累效应,结合烃源岩分布特征推测,柴达木盆地东部凹陷区伊克雅乌汝构造伊深1井天然气应源于上第三系;西部坳陷区尕斯油田尕斯8-6井和尕斯475井天然气应源于下第三系;碱山构造碱1井天然气应源于侏罗系,碱山构造碱2井的天然气应源于上第三系;北缘块断带南八仙油气田仙试1井的天然气应源于侏罗系;南八仙油气田仙试8井和马北构造马北1井的天然气可能主要源于侏罗系。更多还原

【Abstract】 In order to determine the new exploratory formation,this paper analyzed the He and Ar isotopic composition of 8 natural gas samples from 5 oil fields or structures in the Qaidam Basin and discussed their tracing significance in tectonic backgrounds,geothermal flow and gas source.The research shows the results as follows: ① the 3He/4He values of natural gases in the studied area is distributed on the range from 2.0×10-8 to 5.48×10-8,in an order of 10-8,averaging 3.7×10-8,reflecting the characteristic of the typical helium isotope of crust origin.②The geothermal flow values calculated based on 3He/4He ratios range from 41.2 to 48.2 mW/m2,averaging 44.9 mW/m2,which is lower than the average ones in the eastern China,indicating stable tectonic backgrounds of the Qaidam Basin.③Based on an aging effect of natural gas 40Ar/36Ar and integrating the distribution of source rocks,it deduces that gases from the well Yishen 1 in the Yikeyawuru structure in the eastern depression area were derived from the Upper Tertiary;gases from the well Gasi 8-6 and Gasi 475 in the Gasi oil field in the western depression area were derived form the Lower Tertiary; gases from the well Jian 1 in the Jianshan structure were sourced form the Jurassic and that from the well Jian 2 in the Jianshan structure from the Upper Tertiary;gases from the well Xianshi 1 in the Nanbaxian oil and gas field in the northern fault block zone was derived from the Jurassic;gases from the well Xianshi 8 in the Nanbaxian oil and gas field and the well Mabei 1 in the Mabei structure were also mainly sourced from the Jurassic.The knowledge about the gas sources is of important significance to find new natural gas explored strata in the Qaidam Basin.更多还原