Abstract: It is frequently occurred that logging instruments fail to run to the required depth after cementing, caused by the changes of drilling fuid properties and mud contamination because of poor sealing of drill pipe rubber plug. This in turn requires drifting and repeated logging, leading to cost rise and additional problems.A new spacer fluid, HY-100 is developed, which mainly contains a suspending agent made of cationic polymer. Field uses in 704 wells in Huabei, Daqing, and Jilin oil fields were successful.