摘要
本文根据广东省三水盆地天然气中He,Ar,CO_2和N_2的稳定同位素地球化学特征,探讨了该区非烃天然气组分的成因以及大地热流。天然气中~3He/~4He值为(1.60—6.39)×10^(-6),^(40)Ar/^(36)Ar值为450—841,δ^(13)C_(Co_2)的变化范围为-20—-2‰,δ^(15)N在-58—+95‰之间。天然气同位素地球化学特征表明三水盆地有较强的地球深部流体(物质和热)向上溢出。富含非烃组分的气藏中,大部分He,Ar,N_2来自地球深部,CO_2则主要由岩石化学反应生成。烃类天然气藏中非烃组分主要来自地壳中放射性成因的~4He、^(40)Ar和有机质热分解产生的CO_2、N_(20)根据~3He/~4He值估算大地热流值(Q)为72—82mWm^(-2),其中一半以上可能来自上地幔。
Heat flow and the origin of non-hydrocarbons in natural gases are discussed in terms ofthe isotope geochemical characteristics of Ar, He, CO_2 and N_2 in natural gases from the San-shui Basin, Guangdong Province, China. ~3He/~4He ratios have a range of (1.60--6.39)×10^(-6),and ^(40)Ar/^(36)Ar ratios range from 450 to 841. The δ^(13)C(PDB) values of carbon dioxide rangefrom --20 to --2‰ δ^(15) N(air) ratior have a wider range of --57 to +95‰. The isotope geo-chemical characteristics of non-hydrocarbons ndicate that most of the He, Ar and N_2 in thegas reservoirs are enriched in non-hydrocarbons derived from the upper mantle, and carbondioxide was derived mainly from carbonate strata. Non-hydrocarbons in gaseous hydrocarbonreservoirs consist mainly of crustal radiogenic He and Ar and some amounts of mantle-derivedHe, Ar, and carbon dioxide depleted in ^(13)C and nitrogen generated from the decompositionof organic matter in the strata. Based on the relationship between heat flow (Q) and ~3He/~4He ratio in natural gases, va-lues of Q for the study area have been calculated. The calculated mean value of Q (78 m-Wm^(-2)) is coincident with that for the areas which have experienced upper mantle uplifting inHuabei and the Tanlu rift zone (77 and 88 mWm^(-2), respectively). More than 60 percent ofLeat flow in the Sanshui Basin was derived from the mantle.
出处
《地球化学》
CAS
CSCD
北大核心
1993年第1期28-34,共7页
Geochimica
基金
国家自然科学基金
