摘要
基于银额盆地查干凹陷巴音戈壁组一段、二段烃源岩岩性、古生物化石、热演化程度对比结果，首次提出C29重排谷甾烷不受烃源岩热演化程度影响，主要与烃源岩原始母质中植物的贡献有关的观点。C29重排谷甾烷在植物炭屑质量分数高的巴一段灰黑色、深灰色泥岩中含量高，在植物炭屑质量分数低的巴二段深灰色泥岩中含量低，可作为指示母质类型的地球化学指标来进行油源对比。采用C29重排谷甾烷含量和成熟度指标——C29规则甾烷异构化值，开展查干凹陷2个重点区带源藏对应关系研究，结果表明：乌力吉构造带深层巴一段、二段稀油具有高C29重排谷甾烷含量、高成熟度特征，来自巴一段烃源岩；乌力吉构造带浅层苏红图组和银根组稠油具有中等C29重排谷甾烷含量、中等成熟度的“混源”特征，来自巴一段和巴二段烃源岩。中央构造带西翼苏红图组稀油具有C29重排谷甾烷含量低、成熟度较低的特征，为巴二段烃源岩“单源”供烃；中央构造带东翼目前勘探程度最低，巴二段和苏红图组发现的稀油具有中等C29重排谷甾烷含量、中等成熟度的“混源”特征，由巴一段和巴二段烃源岩“双源”供烃，为勘探潜力区。
Abstract
According to the comparison results of source rock lithology, paleontological fossil, and thermal evolution degree in the Ba1 and Ba2 members of Bayingebi Formation in Chagan Depression of Yingen-Ejinaqi Basin, it was proposed that the C29 rearranged sitostane was controlled by the contribution of plants in the original parent material of source rock, which was not affected by the degree of thermal evolution of source rocks for the first time. C29 rearranged sitostane was used to oil source contrast based on the high content of grey-black and dark gray mudstone with high plant carbon dust in Ba1 Member and the low content of dark gray mudstone with low plant carbon dust in Ba2 Member, which was an important geochemical index indicating the parent material type. The oil source relationship of two key tectonic belts in Chagan Depression was studied by using the content of C29 rearranged sitostane and maturity index with the value of C29 regular sterane isomerization, the results showed that in the deep reservoir of Wuliji tectonic belts, the characteristics of normal oil in Ba1 and Ba2 members was high content of C29 rearranged sitostane and high value of C29 regular sterane isomerization, which means they were from the source rock of Ba1 Member. While the characteristics of heavy oil in Suhongtu and Yingen Formation was medium content of C29 rearranged sitostane and medium value of C29 regular sterane isomerization, which means they were mixed reservoir from the source rock of Ba1 Member and Ba2 Member. In the western of central tectonic belt, the characteristics of normal oil of Suhongtu Formation was low content of C29 rearranged sitostane and low value of C29 regular sterane isomerization, which means it was from the source rock of Ba2Member. While in the eastern of central tectonic belt, the characteristics of normal oil of Ba2 Member and Suhongtu Formation was medium content of C29 rearranged sitostane and medium value of C29 regular sterane isomerization, which means it was a mixed reservoir from the source rock of Ba1 Member and Ba2 Member. The eastern of central tectonic belt was least explored and it was a favorable exploration potential area for the good condition of double source hydrocarbon supply.
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