辽河盆地黄沙坨油田原油中氦同位素的来源及其地质意义

Sources and Geological Significance of ^3He/^4He Ratios of Crude Oils from the Huangshatuo Oilfield in Liaohe Basin

辽河盆地黄沙坨油田原油样品中氦、氖和氩稀有气体同位素值的测试研究结果显示:①黄沙坨油田原油中稀有气体3He/4He(Rc)分布于2.61×10-6～3.50×10-6,平均3.06×10-6,具有幔源氦混入的特征,幔源氦的侵入份额为20.13%～30.24%,表明该区具有切割至上地幔的深大断裂;②据3He/4He计算,辽河盆地黄沙坨油田大地热流值分布于75.3～77.3mWm-2之间,平均76.4mWm-2,与我国中部、西部盆地相比该地区具有较高的大地热流值,对有机质的成熟与成烃较有利;③上述研究结果表明原油氦同位素的研究与天然气中氦同位素的研究相似,可为大地构造背景、大地热流、油气来源和演化判识等方面的研究提供有益的科学信息。

Based on analyses of He, Ne and Ar isotopes of crude oil samples from the Liaohe Basin, the authors have reached the following conclusions： （1）the ^3He/^4He（Rc） values of the crude oil samples in the study area are distributed in the range of 2.61×10^-6-3.50×10^-6, with an average of 3.06×10^-6 and in an order of 10^-6, showing characteristics of the mantle-derived H elium input, whereas the percentages of the mantle-derived helium are distributed between 20.13% and 30.24%, showing the existence of deep faults that cut into the mantle in the study area; （2）the geothermal flow values calculated based on ^3He/^4He ratios range from 75.3 to 77.3 mW/m^2, with an average of 6.4 mW/m^2, which is higher than the average values of the basins in central and western China, and such a condition is beneficial for the generation of hydrocarbon; （3）the above results show that the application of the research method of ^3He/^4He values in crude oil can provide much information for inferring the sources of natural gas and oil, the tectonic backgrounds and the geothermal flow values.