Abstract: To resolve difficulties and poor centralization in running casing with conventional rigid centralizers,improve the cementing quality and guarantee fracture effect in long horizontal well of unconventional well,the φ139.7 mm hydraulic centralizer had been developed which,different from the domestic lamination core and small size centralizer,features easy running,self-locking,high centralizing strength,and could meet the high pressure fracturing demands of unconventional well.It had been applied in unconventional block of Shengli Oilfield by the mode of double ball seat+hydraulic centralizer string and ball dropping expansion technique,the friction of hydraulic centralizer on drill string and cementing quality were analyzed,which proved that friction on hydraulic centralizer string was completely below that on rigid centralizer string,hydraulic centralizer could greatly improve cementing quality of horizontal section,and it provided strong technical support for unconventional well cementing.