苏北盆地混源油气地球化学与成藏特征

Geochemical Characteristics and Hydrocarbon Accumulation Mechanism of Mixed Oils in Subei Basin

金湖凹陷原油族组成具典型未熟-低熟油的特征,普遍检出热稳定性低的化合物,碳优势指数、奇偶优势与藿烷成熟度参数体现成熟特征,但甾烷成熟度参数存在明显变化,原油来自4个不同成熟度的运聚场,定量计算了不同地区的未熟油混合比例。盐城凹陷凝析油具与湖相原油和海相原油相似的混源特征,轻质组分反映一种高成熟演化特征,中等组分体现出未熟-低熟的特征,重组分反映达到或超过了主要生油演化阶段,下生上储成藏模式使高成熟天然气对成熟原油进行了气洗作用,造成了凝析油的"特殊"特征。

Oils in Jinhu sag are characterized by the typical immature-low mature, and some compounds with low thermal stability are identified. Carbon number preference index, odd-even predominance and hopane maturity show little difference of maturity between the oils. But the variation of sterane isomerisation parameter and source analysis indicates hat four migration and accumulation patterns with different maturities can be classified. Quantitative analysis shows that different percentage of immature oils is mixed with normal oils in Jinhu sag. The condensate associated with natural gas in Yancheng sag suggests both similarity and difference with lacustrine oils and marine oils. The light compositions of condensate are presented high mature, while the middle compositions assume immature to low mature and the heavy compositions show mature. The pattern of hydrocarbon accumulation with sources in lower strata and reservoirs in upper ones allows the mature oils to be scrubbed by the high mature gas, which appears the special feature of gas condensate.