应用高分辨率质谱分析苏丹高酸值原油成因

Formation mechanism analysis of Sudan high acidity oils by electrospray ionization fourier transform ion cyclotron resonance mass spectrometry

苏丹Muglad和Melut盆地是苏丹乃至整个中、西非剪切带最富含油气的盆地,所发现的原油主要为中质油(重度为20°～34°API),其次为重质油(重度小于20°API),普遍高含沥青质、高含蜡、高酸值、低含硫。为了探讨高酸值原油的成因,选择了苏丹地区18个不同酸值的原油样品,尝试高分辨率质谱分析上述原油有机酸的组成。结果表明,高酸值原油的有机酸主要由环烷酸组成;环烷酸的平均相对分子质量随降解作用程度增加而增大,分子碳原子数分布范围变宽;环烷酸以一环、二环、三环环烷酸为主。生物降解作用是形成高酸值原油的主要原因。

Crude oils produced from the Muglad and Melut basins,which are hydrocarbon-rich basins in Sudan,even in the Central-West African Shear Zone(CASZ),display unusually high total acid number values(TAN,up to 16 mg KOH/g oil) with high wax content and asphaltene.In order to probe the formation mechanism of Sudan high TAN oils,the authors picked up 18 oils with different TANs to analyze the composition of organic acids of crude oil by electrospray ionization fourier transform ion cyclotron resonance mass spectrometry.The research results indicated that the organic acid is consisted mainly of naphthenic acid which relative molecular weight increased gradually with the increment of biodegradation degree.The naphthenic acid of high TAN oils is consisted mainly of mono-cyclic,bi-cyclic,tri-cyclic naphthenic acid.The key reason for forming high TAN oils is only biodegradation.