【摘要】 <正> 前人对生油岩中轻烃的研究工作表明:甲烷具有多种成因;而 C₂以上轻烃直接由生物体合成的可能性甚小,它们可能与重烃相似,是在分散沥青和干酪根聚合物形成与演化的过程中通过热降解或热裂解作用产生的。笔者用气相色谱法研究了取自某盆地一口探井的罐装岩屑样品中的 C₁—C₇轻烃组成,对轻烃的各项比值在不同埋藏深度的变化趋势进行了初步探讨。研究结果表明:生油岩中 C₁—C₇轻烃的生成及其分布,可能是研究有机质热演化程度的有效标志。更多还原

【Abstract】 C₁-C₇ light hydrocarbon of 150 canned cutting samples collected from atest well are analysed with capillary GC so as to study the regularity how lighthydrocarbon composition varies with buried depth.Light hydrocarbon is mainly methane when rocks yielding it are buriedless than 2,650m;the ratio of（C₂-C₄）/（C₁-C₄）increases rapidly from lessthan 30% to 60% when buried depth is about 2,650m;but C₄-C₇ turn to bethe primary components when buried more than 3,650m.It is obvious that with the increase of buried depth,the content of N-alkanaand cycloalkane increases gradully while the iso-alkane decreases.Within the depth of 3,750m,cyclohexane/cyclopentane ratio increases withthe increase of the depth,suggesting that cyclohexane is more stable than cy-clopentane in thermodynamics.But the ratio shows obviously a decrease ten-dency with the increase of depth,when it is buried bellow 3,750m,this ap-pears to be related to the preferential aromatization of cyclohexane.In accordance with the mass-producing of wet gas,the methylcyclopentane/cyclopentane and methylcyclohexane/cyclohexane ratios get the maximum va-lues,similar variation is also observed in the dimethylcyclopentane/cyclo-pentane ratio.The ratio of 1,1-dimethylcyclopentane to isomers of dimethylcyclopentaneis usually less than 0.1 and changes slowly when the buried depth is shal-lower,but increases rapidly to more than 0.3-0.4 when buried greater than3,300m.It is believed that differential evolution and maturation are probably thegeneral characters in the evolution process of organic matter,and various ra-tio of light hydrocarbons mentioned above may be considered as indices ofmaturity.更多还原