准噶尔盆地哈山地区生物降解原油地化特征

Geochemical Characteristics of Biodegraded Crude Oil in the Hashan Area of the Junggar Basin

摘要: 哈拉阿拉特山地区位于准噶尔盆地西北缘，蕴藏着丰富的浅层油气资源。通过色谱–质谱分析发现这里的原油普遍遭受过不同程度的生物降解作用，其物性及化学成分会发生改变，增加分析难度。本次研究以生物降解原油为研究对象，基于正构烷烃、甾烷、萜烷类生物标志化合物特征，分析生物降解作用对不同化合物的影响。结果表明，随生物降解程度增强，原油中胶质与沥青质含量持续增加，正构烷烃逐渐消失，色谱图中“鼓包”(UCM)显著增大且位置前移，而饱和烃含量未呈现明显规律性变化，重度降解原油仅残留异构烷烃与不可分辨化合物。25-降藿烷的出现可作为生物降解等级超过5级的重要标志。

Abstract: The Halashan area, located on the northwestern margin of the Junggar Basin, is rich in shallow oil and gas resources. Chromatography-mass spectrometry analysis revealed that crude oil here has generally undergone varying degrees of biodegradation, altering its physical properties and chemical composition, making analysis more challenging. This study examined biodegraded crude oil and analyzed the effects of biodegradation on various compounds based on the biomarker characteristics of n-alkanes, steranes, and terpenes. The results showed that with increasing biodegradation, the content of colloids and asphaltenes in the crude oil increased, n-alkanes gradually disappeared, and the “bump” (UCM) in the chromatogram significantly increased and shifted forward. However, the content of saturated hydrocarbons showed no significant regularity, and only isoalkanes and unresolved compounds remained in severely degraded crude oil. The presence of 25-norhopane can be used as an important indicator of biodegradation exceeding level 5.