Characteristics of Jurassic Source Rocks and Direction of Petroleum Exploration in Yabulai Basin,China

The Jurassic offers a good exploration objective in the Yabulai Basin which is poorly explored. Based on the geochemical study of the Jurassic potential source rocks,it can be concluded that mudstone of the Lower Xinhe Formation in the Middle Jurassic is the main source rock which deposited in the lacustrine facies,the Qingtujing Formation is moderate source rock,and Shazaohe Formation is the poorest source rock.Results show that the Lower Xinhe Formation source rock has large thickness,ranging from 35to 1 174m,and it contains high TOC with an average of 1.61%.It is dominated by type Ⅱ organic matter which is at mature stage.In addition,a lot of interbedded lamalginite and mudstone are present in the source rock from Xiaohuzi sub-depression,indicating that the Lower Xinhe Formation source rock has a good hydrocarbon potential.In the plane,the hydrocarbon potential of the Lower Xinhe Formation source rock in Xiaohuzi and Yanchang Sags is better than that in Suotuo Sag.The main reasons are that source rock in the Suotuo Sag was shallowly buried and at the stage of low mature period.The structure high points of the southern basin or the lithologic trap developed locations in deep depression are the main targets for the latest petroleum exploration.The analysis above can also be used for analogical study of the Jurassic source rocks in the other parts of the northwest China.