混源气的组分与碳同位素特征研究  

Investigation on Chemical Compositions and Carbon Isotope of Mixed Gases from Different Sources

作　　者：曾庆辉[1,2] 

机构地区：[1]中石化胜利油田分公司临盘采油厂,山东临邑251507 [2]中国科学院化学研究所,北京100190

出　　处：《石油天然气学报》2010年第6期1-5,共5页Journal of Oil and Gas Technology

基　　金：中国科学院知识创新工程重要方向项目(kzcx2-yw-q05-06)

摘　　要：以两种干酪根(Ⅰ型与Ⅲ型)热模拟气作为单元组合,进行不同条件的混合,考察了其混合气组成与同位素的变化。结果表明:不同来源天然气混合可导致天然气组成与碳同位素的变化,混合的两种气体组分与碳同位素差别越大,对混合气的影响越大。相近成熟度的Ⅰ型与Ⅲ型气混合,虽可在一定程度上导致天然气同位素变化,但不会导致碳同位素序列倒转。同位素倒转仅出现在某些特殊条件,如在很高成熟度Ⅲ型气中混入少量低、中成熟Ⅰ型气,可导致混合气δ13C2与δ13C3、甚至δ13C1与δ13C2倒转。在高成熟Ⅰ型气中混入少量低成熟Ⅲ型气可导致δ13C1-δ13C2值与δ13C2-δ13C3值变小,但一般不会引起碳同位素倒转。不同来源天然气的混合导致天然气地球化学指标存在多解性,在天然气成因评价时应当予以重视。Thermal pyrolysis experiments for gas generation from two kerogen samples(Type Ⅰ and Type Ⅲ)were conducted in a confined system,the mixing of the generated gases were investigated.The results indicate that gases mixing with different origins would cause an obvious variation in chemical compositions and carbon isotope.The greater the difference between the two mixed gases and their carbon isotope was,the stronger the influence on the mixed gas was.Mixing the gases of Type I and III with similar maturities could result in variation of the carbon isotope of natural gas to some extent,but could not result in the carbon isotope reversal.The isotope reversal occurred only in very special situations.For instance,high-mature Type III gas was mixed with small amount of low-maturity Type I gas could usually lead to the reversal between δ13C2 and δ13C3,even the reversal between δ13C1 and δ13C2.Mixing high-maturity type I gas with low-maturity type III could result in a less value of δ13C1-δ13C2 as well as δ13C2-δ13C3 as compared with its two single gases,but the isotope reversal was not usually induced.It is realized that mixing different gases would result in multi-explanation of its geochemical indexes,which should be considered in origin identification of field gases.The study result can provide an important guidance for the evaluation of mixed gases.

关 键 词：混源气 气体组分 碳同位素 同位素倒转 

分 类 号：P618.13[天文地球—矿床学]