石油二次运移的分子地球化学特征

MOLECULAR GEOCHEMICAL CHARACTERISTICS OF THE SECONDARY PETROLEUM MIGRATION

该文采用索氏抽提法获得模拟实验中不同运移距离的油样,用GC/MS对这些油样中的饱和烃、芳烃馏分进行了分析。正构烷烃、烷基菲、烷基硫芴以及烷基芴在石油二次运移初期分馏效应的研究结果表明:极性非常小的正构烷烃进入充满水的疏导层后,受粘土矿物物理吸附的影响较大,导致nC18-/nC19+的峰值比在一定的运移距离内呈现递减的趋势,当物理吸附达到平衡后,nC18-/nC19+峰值比则有明显的递增趋势;极性较大的芳烃馏分在地质色层效应的影响下,烷基菲、烷基硫芴、烷基芴表现出明显的高分子滞后的运移分馏效应;正构烷烃和芳烃馏分在石油二次运移初期首先受到物理吸附的作用,并且这种作用对正构烷烃在时间、空间上的影响远大于芳烃馏分。这些实验认识为合理有效地评价油气运移过程提供了有力的研究依据。

Oil samples of different migration distances were obtained from the extraction of the simulation experiment. The saturated and aromatic hydrocarbon fractions in these oil samples were made GC/MS analysis. The results of the stuey on the fractionation effects of nalkane, alkyl phenanthrene, alkyl sulfur fluorene and alkyl fluorene in the early stage of the secondary petroleum migration revealed that the nalkane with very little polarity was subjected greater influences from the physical adsorption of clay mineral after entering drainage layers full of water. This resulted in the decreasing trend of nC18-/nC19+ peak value ratio within a certain migration distance. When the equilibrium of physical adsorption was reached, the peak value ratio of nC18-/nC19+ had an obvious increasing trend. Affected by geologic chromatographic effects, alkyl phenanthrene, alkyl sulfur fluorene and alkyl fluorene in the aromatic fractions with greater polarity presented obvious migration fractionation effects of highmolecular hysteresis. The nalkane and aromatic fractions were subjected physical adsorption at first in the early stage of the secondary petroleum migration, and the action on nalkane was far greater than on aromatic fractions either in time or in space. The knowledge obtained from the experiment provided powerful research basis for the rational and effective evaluation of hydrocarbon migration processes.