干酪根与芳烃化合物固—液有机质相互作用机理研究

Solid-liquid organic matter interaction mechanism between kerogen and aromatic compounds

地质条件下,烃源岩中最初生成的油气,达到饱和后,才能排出运移,而干酪根对烃类的吸附作用,是影响含油饱和度的重要因素。热解作用产生的烃类物质会与干酪根大分子发生相互作用,研究固体干酪根有机质对液态烃的溶解和吸附能力,可以明确烃源岩对烃类化合物的选择性滞留及生排烃特征。芳烃是石油烃类化合物的重要组成部分,在干酪根三维模型的基础上,利用Autodock软件将不同类型的芳烃化合物分子(包括苯、稠环芳烃和稠环芳烃衍生物)与不同成熟度的干酪根分子进行半柔性对接结算,计算两者结合所需的吉布斯自由能,研究芳烃化合物与干酪根结合的特征,从分子层面上研究干酪根吸附芳烃化合物的机理,揭示固—液有机质相互作用的本质。当与相同成熟度的干酪根结合时,稠环芳烃的分子质量越大、化合物中的甲基数量越多、分子缩合度越高,与干酪根分子结合所需的吉布斯自由能越低;芳烃化合物与干酪根分子之间相互作用受到芳烃的分子质量、分子缩合程度以及体系内甲基数量3个因素的影响。处于生烃高峰后,芳碳甲基含量较高的干酪根对芳烃的吸附能力较强;分子质量大、缩合度高的稠环芳烃及其衍生物与干酪根的结合能力较强;常规连接的小分子芳烃化合物在干酪根中的滞留能力较弱,更易发生排烃作用,运移富集成藏。

Under geological conditions,the initial generation of oil and gas in source rocks reaches saturation before being expelled and migrating,with the adsorption of hydrocarbons by kerogen being a key factor influencing oil saturation.The hydrocarbons produced by pyrolysis interact with kerogen macromolecules.Understanding the solvency and adsorption capacities of solid kerogen organic matter for liquid hydrocarbons can clarify the selective retention of hydrocarbons by source rocks and their characteristics in hydrocarbon generation and expulsion.Aromatic hydrocarbons are crucial components of petroleum hydrocarbons.Based on a three-dimensional model of kerogen,this study employed Autodock software to perform semi-flexible docking calculations between different types of aromatic hydrocarbon molecules(including benzene,polycyclic aromatic hydrocarbons,and their derivatives)and kerogen molecules of varying maturities.The Gibbs free energy required for their binding was calculated to study the characte-ristics of the interaction between aromatic hydrocarbons and kerogen.This study investigated the mechanism of kerogen adsorption of aromatic hydrocarbons at the molecular level,revealing the nature of solid and liquid organic matter interactions.When binding with kerogen of the same maturity,the larger the molecular weight of the poly-cyclic aromatic hydrocarbons,the greater the number of methyl groups in the compound,and the higher the degree of molecular condensation,the lower the Gibbs free energy required for binding with kerogen molecules.The interaction between aromatic hydrocarbons and kerogen molecules was influenced by three factors:the molecular mass of the aromatic hydrocarbons,the degree of molecular condensation,and the number of methyl groups in the system.After reaching the peak of hydrocarbon generation,kerogen with higher content of aromatic carbon methyl groups showed a stronger adsorption capacity for aromatic hydrocarbons.Polycyclic aromatic hydrocarbons and their deriva-tives with larger molecular mass and higher degrees of condensation demonstrated stronger binding abilities with kerogen.Conversely,smaller aromatic molecules with conventional connectivity exhibited weaker retention capacities in kerogen,making them more prone to hydrocarbon expulsion,migration,and accumulation into reservoirs.