鄂尔多斯盆地姬塬油田延长组原油性质与来源分析

Study on the Property and Origin of Crude Oil of Yanchang Formation in Jiyuan Oilfield,Ordos Basin

通过原油与油田水物理性质、原油与烃源岩族组成、饱和烃气相色谱以及萜烷与甾烷等生物标志化合物特征的多项地球化学指标对比,表明鄂尔多斯盆地姬塬油田延长组长8、长6、长4+5等油层组原油性质较为复杂,其成熟度、母源氧化-还原环境及母质类型等方面存在显著差异。烃源岩评价也显示长9、长8、长7、长6、长4+5段的暗色泥岩有机质质量和类型有所差别,但均具备生排烃能力。油源对比结果进一步证明:成藏过程存在多套油源混源供油的成藏效应,其中长8油层组原油主要来源于长7—长8段烃源岩;长6油层组原油主要来源于长7—长6段烃源岩;长4+5油层组原油存在长7、长6及长4+5段多源烃源岩的贡献。

Based on the comparison of multiple physicochemical properties including the property of crude oil and oilfield water,group composition of crude oil and hydrocarbon source rock,gas phase chromatography of saturated hydrocarbon and the characteristics of terpane,sterane and other biomarkers,the results showed that the properties of crude oil were especially complex for Chang-4＋5,Chang-6 and Chang-8 of Yanchang Formation in Jiyuan Oilfield,Ordos Basin;there were obvious differences in the maturity,source rock depositional redox environment and type.The appraisal of hydrocarbon source rock indicated that the quality and type of organic matter of dark mudstone for Chang-4＋5,Chang-6,Chang-7,Chang-8 and Chang-9 of Yanchang Formation were different,but all had the ability of hydrocarbon generation and expulsion.The comparison of oil sources further proved that there were multiple accumulation effects of oil supply with mixed sources in the accumulation process;the crude oil of Chang-8 came from hydrocarbon source rock of Chang-7-Chang-8;the crude oil of Chang-6 came from hydrocarbon source rock of Chang-7-Chang-6;the crude oil of Chang-4＋5 came from multiple hydrocarbon source rocks of Chang-7,Chang-6 and Chang-4＋5.