石油与天然气地质 ›› 2010, Vol. 31 ›› Issue (3): 353-359.doi: 10.11743/ogg20100313

• 石油与天然气地质 • 上一篇    下一篇

柴达木盆地西部原油地球化学特征对比

  

  • 出版日期:2010-08-24 发布日期:2010-09-02

G eochem ical characteristic comparison of crude oil samples from the western Qaidam Basin

  • Online:2010-08-24 Published:2010-09-02

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被引次数

50

摘要：

柴达木盆地西部地区各油田所产原油在成因上大多属咸水湖相，因而具有咸水湖相成因原油某些共同的地球化学特征，如低的姥植比和正构烷烃的偶碳优势等。对比后发现，柴西南区所产原油在正构烷烃系列分布特征上基本都具有nC 37 优势、姥植比相对较低且伽马蜡烷含量丰富，而柴西北区所产原油则在正构烷烃系列分布特征上大多没有nC 37 优势、姥植比相对偏高且伽马蜡烷含量明显偏低，这表明柴西南区与北区的原油其烃源岩具有不同的地球化学特征。依据原油中的nC 37 优势与姥植比之间负相关、与伽马蜡烷指数之间正相关这一现象，推测原油中正构烷烃系列的nC 37 优势主要受控于沉积环境的性质，高盐度和强还原的沉积环境是导致原油中出现nC 37 优势的主要地球化学因素。

关键词: 正构烷烃, 伽马蜡烷, 姥植比, 沉积环境, 原油, 柴达木盆地西部

Abstract:

Crude oils produced from the oilfields in western Qaidam Basin are sourced from saline lacustrine faˉcies，thus they share certain geochem ical characteristics such as lower Pr/Ph ratio and predom inance of even carbon in normal alkanes.However，a comparison of the samples from the south and north parts of the western basin reveals that crude samples from the south part feature in an obvious nC 37 predom inance in normal alkanes，lower Pr/Ph ratio and high gammarcerane index，while those from the north part has no nC 37 predom inance in normal alkanes，but higher Pr/Ph ratio and lower gammacerane index，indicating differences in geochem ical characteristics of the source rocks between the two parts of the basin.It is noted that a negative correlation beˉtween nC 37 predom inance and Pr/Ph ratio，and a positive correlation between nC 37 predom inance and gammaceˉrance index couldmean that the nC 37 predom inance be related to the nature ofdepositional environment and that a strongly reduced and highly saline environment is themain factor causing an obvious nC 37 predom inance in the crude samples.

Key words: normal alkane, gammacerane, Pr/Ph ratio, depositional environment, crude oil, western Qaidam Basin