准噶尔盆地中部1区块原油轻烃地球化学特征

Geochemical Characteristics of Light Hydrocarbons in Crude Oils from No.1 Area of Central Junggar Basin

通过对准噶尔盆地中部1区块与相邻油田原油中轻烃分布与组成特征的系统对比研究,发现中部1区块原油的轻烃以富含甲基环己烷为特征,其甲基环己烷指数基本都大于50%,且具有相对较高的姥植比。这明显不同于相邻的石西油田和莫北油田的原油,揭示出中部1区块原油中具有一定量陆源有机质的贡献。这与前人依据生物标志化合物和碳同位素的分析资料所得出的油源对比结果一致。利用2,4-二甲基戊烷/2,3-二甲基戊烷值计算的原油生成时镜质体反射率结果表明中部1区块原油的成熟度高于临近的石西油田和莫北油田的原油,表明盆地腹部主力烃源岩层中有机质成熟度相对偏高。由此可见,原油轻烃在研究其来源、成因和成熟度等方面具有很高的实用价值。

System comparative studys of the distributions and compositions of light hydrocarbons in crude oils from No.1 area and adjacent oilfields in Junggar basin show that abundant methyl cyclichexane exists in the crude oils with methyl cyclichexane index（MCHI） more than 50% and higher Pr/Ph ratio,which are very different from crude oils from Shixi and Mobei oilfields.This implies that terrestrial matter from higher plants plays a significant role during the generation of the crude oils from No.1 area,and it is consistent with the results of the literature by geochemistry methods of biomarkers and carbon isotope.According to the relationship between the 2,4-DMC5/2,3-DMC5 ratio and the temperature of oil generation,it suggests that the maturity of crude oils from No.1 area is higher than those from Shixi and Mobei oilfields,indicating higher maturity of the organic matter in main source rocks of central Junggar basin.Therefore,it′s very useful of the light hydrocarbon from crude oils for the study of its origin,causes and maturity.