Tight oil generally refers to the oil stored in the tight sandstone reservoir or tight carbonate reservoir that the overburden matrix permeability is less than or equal to 0.1mD(equivalent of about air permeability less than 1.0 mD)(Zeng et al.,2014).The tight oil resources are widely distributed in China,among them the Chang 6-Chang 8 of Yanchang formation in Ordos basin is an important tight oil