Abstract: Fifty four samples of Tertiary source rock and crude oil from the western part of Qaidam Basin have been analyzed geochemically.Isomerization level of C₂₉-sterane was taken as the maturation scale.We observed a whole evolutionary series from immature and lowmatured to matured and highly matured oils which correspond to the products at different evolutionary stages of the organic matter in source rocks.The wide distribution of immature oil and the existence of a whole series of maturation in Tertiary continental deposit basins in China have an important geochemical feature.The observation breaks through the limitation of the theory of generating hydrocarbon from kerogen.It has the practical significance in providing a scientific basis for forecasting petroleum resources by maturation classification.The oils already discovered in Qaidam Basin are mostly under matured,and exploration for oils of other evolutionary stages,especially the highly matured oil,is promising.

摘要： 对柴达木盆地第三系54个生油岩和原油样品,进行系统的地球化学检测,并以生物标记物中C₂₉甾烷的异构化程度作为成熟度标尺,发现该盆地的原油有一个从未成熟、低成熟、成熟直至高成熟的完整演化系列。相应于生油岩中有机质不同成烃演化阶段的产物。现有资料表明,在我国陆相第三系沉积盆地中,未成熟石油和原油熟化系列的普遍存在,是含油上一个重要的地球化学特征。它突破了干酪根成烃学说的局限性,并且在油气的勘探上有着重要的实际意义,为以成熟度分级的油气资源预测提供了科学的依据。研究表明,柴达木盆地目前所发现的石油,大部分是低成熟的,其它成烃演化阶段的石油,特别是深层成熟石油的勘探,还大有可为。