原油中饱和烃化合物在稠油火驱室内实验中的指示作用

On the function of saturated hydrocarbon compounds as indicators in heavy oil reservoir fire flooding laboratory experiments

稠油油藏开发中,火驱是否实现高温氧化已经成为评价开发效果的难点之一。为了认清火驱后原油性质的微观变化特征,借助室内物理模型开展稠油火驱实验,并采用气相色谱-质谱(GC-MS)技术对火驱前后的原油开展饱和烃方面的研究。研究表明:火驱后由于原油中饱和烃组分含量增加,造成轻重比(ΣnC_(21-)/ΣnC_(22+))变大,而Pr/nC17、Ph/nC18降低,Pr/Ph比值和OEP值基本不变;甾烷系列化合物的分布特征和含量变化是判断火驱高温氧化的良好指标,热稳定性较好的孕甾烷和升孕甾烷含量增加明显,甾烷异构化参数C_(29)(ββ)/(αα+ββ)和C_(29)(20S)/(20S+20R)基本保持不变;萜烷系列的三环萜烷/藿烷比值在火驱后增加了近2倍,反映热演化程度的C_(31)(22S)/(22S+22R)比值变化不大;β-胡萝卜烷与γ-胡萝卜烷是判断火驱高温氧化的良好指标,火驱后胡萝卜烷含量大幅降低。因此,通过原油中饱和烃化合物的变化趋势、分布特征、含量变化可有效进行火驱高温氧化的评判,可为稠油火驱开发高温氧化燃烧状态的识别提供有力支持。

Realization of high-temperature oxidation during fire flooding has become one of the difficulties to evaluate the effect of fire flooding in heavy oil reservoirs.To clarify the changing rule of the properties of crude oil after fire flooding,the heavy oil fireflooding experiment was carried out using a three-dimensional indoor physical model,and the saturated hydrocarbons of crude oil after high-temperature oxidation in fire flooding were analyzed by gas chromatography-mass spectrometry(GC-MS).The results showed that after fire flooding,the saturated hydrocarbon content in crude oil increased,causing increased light-to-heavy ratio(Σn^(C21-)/ΣnC_(22+)),decreased Pr/nC17 and Ph/nC18;the distribution characteristics and content variation of sterane series were good indicators for high-temperature oxidation in fire flooding.The contents of pregnane and honopreg⁃nane with high thermal stability increased significantly,and the isomerization parameters of steranes C_(29)(ββ)/(αα+ββ)and C_(29)(20S)(/20S+20R)remained unchanged;the tricyclic terpane/hopane ratio of terpane series increased nearly 2 times after fire flooding,and the C_(31)(22S)(/22S+22R)ratio,which reflected the degree of thermal evolution changed little;β-carotane andγ-carotene were good indicators for high-temperature oxida⁃tion in fire flooding,and carotene contents decreased greatly after fire flooding.Therefore,the change trend,distribution characteristics and content changes of saturated hydrocarbon compounds in crude oil can effective⁃ly evaluate the high temperature oxidation of fire drive,and provide strong support for the identification of com⁃bustion state in fire drive development of heavy oil.