辽河西部凹陷低熟油的高分辨质谱特征及其成因机制

High-Resolution Mass Spectrum Characteristics and Formation Mechanism of Low Maturity Oil in the Liaohe Western Depression

辽河西部凹陷低熟油资源丰富,不同类型稠油的成因机制差异尚不清楚,解决上述问题对辽河稠油的勘探工作具有指导意义。本文采用色谱/质谱(GC/MS)结合傅里叶变换离子回旋共振质谱(FT-ICR MS)技术对辽河西部凹陷北部高升和牛心坨油田低熟油的特征及其成因机制进行研究。高升原油形成于强还原咸水水体,有机质为菌藻类低等生物与陆源的双重贡献。牛心坨原油形成于还原性半咸水水体,有机质来源为低等微生物和陆源有机质双重输入,具有高蜡特征。成熟度参数表明二者均为低熟油。两种低熟油中均检测到N_(1)、N_(1)O_(1)、N_(1)O_(2)、O_(1)、O_(2)、O_(3)、O_(4)化合物,高升低熟油以N_(1)类为主,牛心坨低熟油以O_(2)类为主;前者富含脂肪酸和藿烷酸,后者富含脂肪酸,藿烷酸含量较低,反映两种原油成因机制的差异。高升低熟油中大量的藿烷酸表明其生烃母质在早期成岩作用阶段经历了细菌改造作用,低熟油为细菌改造有机质低温生烃和藻类类脂低温生烃混合成因机制。牛心坨低熟油富含脂肪酸和高等植物蜡质,成因机制为生物类脂物早期低温生烃。两种低熟油的成因机制,为低熟油成因理论提供了研究方法,有助于完善低熟油成因理论并指导类似盆地低熟油油气勘探。

The Liaohe Western Depression is enriched in low-maturity oil resources,however the formation mechanism of its hydrocarbon remains unclear.GC/MS combined with ESI FT-ICR MS approaches are used to study the characteristics and formation mechanisms of low-maturity oil in the Gaosheng and Niuxintuo areas.The Gaosheng crude oil originated in a strongly reduced saline water environment,with its organic matter sourced from bacteria,algae,and terrestrial sources.The Niuxintuo crude oil originated in a reducing brackish water environment,with its organic matter primarily derived from a combination of microorganisms and terrestrial sources.Notably,the Niuxintuo crude oil exhibits a high wax content.The maturity parameters of the saturated hydrocarbons suggest that both sites contain low-maturity oils.Both low-maturity oils exhibited the presence of N_(1),N_(1)O_(1),N_(1)O_(2),O_(1),O_(2),O_(3),and O_(4) compounds.The Gaosheng low-maturity oil predominantly consists of N_(1) class compounds,while the Niuxintuo low-maturity oil is primarily composed of O_(2) class compounds.The former contains an abundance of fatty acids and hopanoic acid,whereas the latter is characterized by high levels of fatty acids and notably lower hopanoic acid content.This divergence underscores the differences in the formation mechanisms of the two crude oils.The significant presence of hopanoic acid in the Gaosheng low-maturity oil suggests that the hydrocarbon source material underwent reformation by bacterium during the early diagenetic stage.The Gaosheng low-maturity oil results from a combined genetic mechanism involving early hydrocarbon generation from the biological lipids and bacterial reformation of the hydrocarbon source materials.The Niuxintuo low-maturity oil is abundant in fatty acids and higher plant waxes.Its formation mechanism involves early hydrocarbon generation from a significant quantity of biological lipids.Research into the genetic mechanisms of these two types of low-maturity oils provides a methodological approach for studying low-maturity oil genesis.This endeavor enhances our understanding of the genesis of low-maturity oils and provides guidance for exploring low-maturity oil in analogous basins.