芳烃化合物在稠油火驱室内实验中的指示作用

Function of aromatic compounds as indicators in laboratory experiments of heavy oil with fire flooding

火驱是否实现高温氧化是评价稠油油藏火驱开发效果的技术难点之一,为了认清火驱开发过程中原油化学性质的变化规律,采用室内三维物理模型开展了稠油火驱实验,并对火驱高温氧化后的原油开展芳烃气相色谱—质谱方面的研究。火驱后原油中萘系列、菲系列以及稠环芳烃相对含量增加,三芳甾烷相对含量降低;火驱过程中萘系列化合物与菲系列化合物均容易发生脱甲基、甲基迁移以及甲基取代反应,并且β构型萘与菲化合物的热稳定性要明显好于α构型;由于4-甲基二苯并噻吩与1-甲基二苯并噻吩热稳定性的差异,可以用其相对含量的变化和谱图分布特征判断火驱是否高温氧化;稠环芳烃中蒽可以作为火驱高温氧化的标志物,苝/苯并[e]芘、荧蒽/芘、蒽/菲比值的变化也是指示火驱高温氧化的良好指标。原油中芳烃化合物的变化特征与特征性标志物可以作为火驱过程中指示燃烧状态的良好指标,为稠油火驱燃烧状态的判识提供支持。

Identifying whether high⁃temperature oxidation is realized in fire flooding has become one of the technical difficulties in evaluating the effect of fire flooding for heavy oil reservoirs.In order to study how the chemical proper⁃ties of crude oil varied during fire flooding,a series of heavy oil fire flooding laboratory experiments were carried out using a three⁃dimensional physical model,and the gas chromatography-mass spectrometry of aromatics were performed for the crude oil before and after high⁃temperature oxidation during fire flooding.Results show that after fire flooding,the relative contents of naphthalenes,phenanthrenes and polycyclic aromatic hydrocarbons in the crude oil sample increased,while the relative content of tri⁃aromatic steroids decreased.During fire flooding,naphthalenes and phenan⁃threnes were all prone to demethylation,methyl migration and methyl substitution,showing significantly higher thermal stabilities inβ⁃naphthalenes andβ⁃phenanthrenes relative toα⁃naphthalenes andα⁃phenanthrenes.Due to the difference in thermal stability between 4⁃methyldibenzothiophene and 1⁃methyldibenzothiophene,the high⁃temperature oxidation in fire flooding could be identified according to the changes in their relative contents and the distribution characteristics of their spectra.Anthracene in polycyclic aromatic hydrocarbons could be used as a marker of high⁃temperature oxidation in fire flooding,while the changes in perylene/benzo(e)pyrene,fluoranthene/pyrene and anthracene/phenanthrene ratios were also good indicators for high⁃temperature oxidation in fire flooding.As observed from these findings,it can thus be concluded that the variation characteristics and characteristic markers of aromatic compounds in crude oil are good indicators for combustion state during fire flooding,providing favorable support for the identification of combustion state in heavy oil fire flooding.