柯坪隆起阿克苏油苗的地球化学特征及其成因研究

柯坪隆起区是塔里木盆地海相烃源岩露头发育较好的地区之一,但相关的油气研究报道不多。本文详细研究了塔里木盆地柯坪隆起区油苗的有机地球化学特征并进行了相关的成因分析。阿克苏油苗经历了严重的生物降解作用,饱和烃生物标志物所能提供的成因信息十分有限。原油沥青质组分及储层吸附/包裹烃受后生作用影响较小,综合分析油苗沥青质热解产物与吸附/包裹烃的生物标志物及其碳同位素组成可以获得更多有效的成因信息。研究结果表明,阿克苏油苗与其储层吸附/包裹烃具有不同来源。油苗、沥青质以及沥青质热解产物的碳同位素特征与已经报道的多数海相原油及其沥青质较为接近,与典型的寒武系烃源来源的原油差异显著。而储层吸附/包裹烃与已报道的典型寒武系烃源岩来源油的生物标志物及碳同位素特征比较类似,可能形成于较高的热演化阶段。

Geochemistry and its genetic implications of Akesu oil seepage in the Keping uplift

Marine source rocks have long been reported in the Keping uplift from the Tarim basin, however, there were few studies concerned about oil and gas. Geochemical characteristics and its genetic implications of an oil seepage in the Keping uplift of the Tarim basin were well investigated in this work. Akesu oil seepage had undergone severe biodegradation, hence, little genetic information could be concluded from the distribution of biomarkers in saturates. Oil asphaltenes and the absorbed/occluded hydrocarbons are hardly affected by secondary alteration, therefore, a combination of biomarkers and carbon isotopic compositions of the asphaltene pyrolysates and absorbed/occluded hydrocarbons could yield more comprehensive information on the genesis of oils. The results indicate that Akesu oil seepage was derived from different sources of absorbed/occluded hydrocarbons. The carbon isotopic signatures of the oil seepage, the asphaltenes and the pyrolysates of asphaltenes are consistent with that of most marine oils reported in the Tarim Basin, which clearly distinguish them from typical oils derived from Cambrian source rocks. However, the distributional characteristics of both biomarkers and carbon isotopes of the absorbed/occluded hydrocarbons are very similar to that of typical oils sourced from Cambrian rocks. Moreover, it might be inferred that absorbed/occluded hydrocarbons was generated at a high maturity stage from the molecular parameters.