Abstract: In order to solve the cross-contamination problem of cement slurry and drilling fluid in cementing displacement process,a high efficient dual dispersant F-2 has been developed through copolymerization from oxidation and reduction.According to industry standards its performance is evaluated,the results show that rheological properties of polymer drilling fluid and cement slurry after adding dual dispersing agent F-2 are improved.Common cement slurry with dual dispersing agent F-2 is helpful to improve the strength of cement stone.Common cement and polymer drilling fluid with F-2 in different proportions show no sudden change in rheological properties.Optimal dosage of dual dispersing agent F-2 is 0.5%.Then F-2 was tested in two unconventional horizontal wells in Shengli Oilfield.The rheology deterioration of mixed drilling fluid and cement slurry didn’t occur in these tests,and the cementing process was smooth,resulting in premium cementing quality of 95% first interface and above average bond strength of second interface.In comparison,first and second interface cementation quality of the adjacent well without using of dual dispersing agent F-2 is only qualified.The dual-dispersing agent F-2 not only has good double-dispersing effect on cement slurry and drilling fluid,but also provides a new solution to the viscosity increase and thickening of cement slurry in the process of cementing displacement.