柴达木盆地德令哈拗陷中侏罗统烃源岩有机地球化学特征

柴达木盆地德令哈拗陷中侏罗统广泛发育,是该区主要的烃源岩层系.野外地质调查及有机地球化学分析表明,中侏罗统烃源岩主要以油页岩、泥岩、碳质泥岩和煤为主.油页岩有机碳的质量分数平均为7.95%,有机质类型属Ⅰ-Ⅱ型,为好生油岩;泥岩的有机质丰度交化大,但80%以上的样品有机碳的质量分数大于1%,65%样品的有机碳的质量分数...

Organic geochemical characteristics of Middle Jurassic hydrocarbon source rocks in Delingha depression of Qaidam Basin

Middle Jurassic is the main layer system of hydrocarbon source rocks which develops widely in the Delingha depression.Field geological survey and organic geochemical analysis indicate that Middle Jurassic source rocks mainly include oil shale,mudstone,carbonaceous mudstone and coal.The oil shale is a good hydrocarbon-generating rock.Whose mass fraction of organic carbon averages 7.95% and the type of organic matter isⅠandⅡ.Mudstone has different organic matter abundances,but over 80% samples whose mass fraction of organic carbon is more than 1% and over 65% samples whose mass fraction of organic carbon is more than 1.5%.The type of organic matter of mudstone isⅡand Ⅲ1,and the mudstone is evaluated as poor to moderate source rocks.Carbonaceous mudstone whose mass fraction of organic carbon averages 10.89% and the type of organic matter is Ⅲ1 and Ⅲ2,so it belongs to poor hydrocarbon source rocks.The coal is the worst,and it belongs to a non-hydrocarbon source rock or poor hydrocarbon source rock.Most of the organic matter in the outcrop source rocks belongs to unbaked to low maturity,and a little of the organic matter belongs to maturity.It can be deduced that most of the organic matter in a peak period of oil generation and expulsion has a high maturity in the depression.The composition and the distribution of hydrocarbon compounds indicate that Middle Jurassic belongs to a fresh water deposit environment,and there develops semi-deep lake facies and deep lake facies which are good depositional settings to deploy source rocks in the Delingha depression.