Determining oil quality is essential to identifying valuable resource accumulations. However, in new areas of exploration, little information is available on the processes affecting resource quality. Geochemical analyses of oil seeps from frontier regions of New Zealand’s East Coast illustrate an application of underutilized resource quality assessment techniques. Distributions of n-alkanes and isoprenoids reveal biodegradation, and thus potentially lower oil quality in the “southern” versus the “northern” oil seeps. However, sterane and terpane compounds are unaltered, indicating overall biodegradation of these oils is low to moderate. Additionally, lack of 25-norhopane indicates degradation of southern oils may be solely aerobic. Therefore, any subsurface accumulations are potentially unaffected. Investigation of sterane and hopane isomerization ratios and additional sterane and terpane maturity parameters is paired with diamondoid analyses of oil-to-gas conversion and petroleum mixing. Three distinct petroleum mixtures are identified among the sampled seeps: (1) a seep composed of an early/peak oil window component and an intensely cracked condensate/wet gas component, (2) seeps solely containing a peak/late oil window component, and (3) seeps composed of a peak/late oil window component and an intensely cracked condensate/wet gas component. Identified components indicate at least three distinct charges or stages of petroleum generation. Black oil components might indicate actively producing source rock in all regions represented by the seeps. Intensely cracked components indicate petroleum mixing via thermogenic gas infiltration and suggest an effect on oil quality. Important questions concerning migration pathways and timing, ties to New Zealand’s offshore basins, and potential for reservoir entrapment of these petroleum components remain.

中文翻译：

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揭示石油的降解，成熟度，混合和解决对石油前景的影响：来自新西兰边远勘探地区的见解

确定石油质量对于识别宝贵的资源积累至关重要。但是，在新的勘探领域中，关于影响资源质量的过程的信息很少。来自新西兰东海岸边疆地区的石油渗漏的地球化学分析说明了未充分利用的资源质量评估技术的应用。n的分布-烷烃和类异戊二烯显示出生物降解作用，因此与“北部”油渗漏相比，“南部”油质可能降低。然而，甾烷和萜烯化合物未改变，表明这些油的总体生物降解程度低至中等。此外，缺乏25-去甲胆烷表明南部石油的降解可能仅仅是有氧的。因此，任何地下堆积物都可能不受影响。研究甾烷和hop烷的异构化比率以及其他甾烷和萜烯的成熟度参数，并结合类金刚石分析对油气转化和石油混合进行分析。在采样的渗漏中鉴定出三种不同的石油混合物：（1）由早期/峰值油窗成分和强烈裂化的冷凝水/湿气成分组成的渗漏，（2）仅包含峰/后期油窗成分的渗漏物，和（3）由峰/后期油窗成分和强烈裂化的冷凝水/湿气成分组成的渗漏物。所识别的成分表示至少三个不同的装料或石油生产阶段。黑油成分可能表明在渗漏所代表的所有区域都在积极生产烃源岩。强烈裂化的组分表明，石油是通过热成因气体渗透而混合的，并暗示了对油质的影响。有关迁移途径和时机，与新西兰近海盆地的联系以及这些石油组分的储层蕴藏潜力的重要问题仍然存在。所识别的成分表示至少三个不同的装料或石油生产阶段。黑油成分可能表明在渗漏所代表的所有区域都在积极生产烃源岩。强烈裂化的组分表明，石油是通过热成因气体渗透而混合的，并暗示了对油质的影响。有关迁移途径和时机，与新西兰近海盆地的联系以及这些石油组分的储层蕴藏潜力的重要问题仍然存在。所识别的成分表示至少三个不同的装料或石油生产阶段。黑油成分可能表明在渗漏所代表的所有区域都在积极生产烃源岩。强烈裂化的组分表明，石油是通过热成因气体渗透而混合的，并暗示了对油质的影响。有关迁移途径和时机，与新西兰近海盆地的联系以及这些石油组分的储层蕴藏潜力的重要问题仍然存在。