摘要
对胜利油田临南洼陷一块未成熟Ⅱ型烃源岩的干酪根样品进行了封闭体系下高温高压热模拟实验,获取了不同热演化阶段天然气组分和碳同位素值,通过混合配比计算,研究了同源不同成熟度天然气的混合对天然气组分和碳同位素的影响。结果表明,同源不同成熟度天然气的混合改变天然气的组分与碳同位素特征,其变化规律受端元气的成熟度及混合系数的影响,并且端元气体的成熟度差别越大,混合气组分与碳同位素值随混合系数的变化越明显。本研究中,在热模拟实验的成熟度范围内(Easy Ro:0.72%~3.0%),不同混合模型中天然气的δ^(13)C_1与δ^(13)C_2不存在倒转;只有当过成熟天然气和低成熟天然气混合,并且以过成熟天然气为主时,才可能导致δ^(13)C_2与δ^(13)C_3不同程度倒转,但这种混合模型在实际地质条件下很难形成,因此认为只是同源不同成熟度混合作用一般不会造成天然气碳同位素的倒转。本研究对于深刻认识含油气盆地天然气的气源及其碳同位素特征提供了理论依据。
The kerogen of an immature type II source rock sampled from the Linnan Depression of the Shengli Oilfield was used for artificial pyrolysis experiments in this research,and the compositions and carbon isotopic values of pyrolysis gas generated from different maturity stages were obtained.We investigated the effects of a pyrolysis gas“mixture”on its components and carbon isotopic characteristics.The results show that the components and carbon isotopic characteristics of the mixed gas are affected by the maturity and mixing coefficient(f)of the end-member gas,and the larger the difference between the end-member gases is,the more obvious the change of components and carbon isotopic characteristics of the mixed gas with the mixing coefficient(f)is.In this research,within the thermal maturity range of this pyrolysis experiment(Easy%Ro ranges from 0.72%to 3.0%),there is no isotopic reversal ofδ^13C1 andδ^13C2 values in all the mixed models;the isotopic reversal ofδ^13C2 andδ^13C3 emerges only when the mixture is of low-maturity and over-mature gases,and the latter dominates the mixed gas.However,this mixing model is rarely formed in actual geological conditions.Therefore,this research indicates that the mixture of gas generated from the same source rock with different maturities generally cannot cause isotopic reversal.The results of this research provide an additional theoretical foundation to realize the sources and carbon isotopic characteristics of mixed gas in gas-bearing basins.
作者
孙健
程鹏
盖海峰
SUN Jian;CHENG Peng;GAI Hai-feng(Stata Key Laboratory of Organic Geochemistry,Guangzhou Institute of Geochemistry,Chinese Academy of Sciences,Guangzhou 510640,China;University of Chinese Academy of Sciences,Beijing 100049,China)
出处
《地球化学》
CAS
CSCD
北大核心
2018年第4期354-362,共9页
Geochimica
基金
国家自然科学基金(41402116
41603049)
中国科学院战略性先导科技专项(XDB10040300)
国家科技重大专项(2017ZX05008-002-004)
关键词
Ⅱ型烃源岩
热模拟
气态烃
混合
同位素倒转
type II source rock
pyrolysis experiments
gaseous hydrocarbon
mixing
reversal of carbon isotope
