Abstract: Displacement efficiency in the cementation of the horizontal interval is the key for high-quality cementation operations in horizontal wells and rheological properties of spacer fluids are the important parameters affecting displacement efficiency. Large-scale cluster computing platforms in the National Super Computing Center and Fluent software were used to conduct a numerical simulation for displacement in 1,000 seconds during cementation of eccentric annulus in horizontal interval to determine the impact of rheological properties of spacer fluids on displacement interfaces in cementation. Results show that the retention of spacer fluids can be reduced dramatically on both sides of the annulus at low eccentric degrees by reducing flow index of these spacer fluids and displacement efficiencies can be enhanced significantly as displacement interface length reduction, while it can be reduced dramatically or obviously on the wider side of the annulus at medium and high eccentric degrees, respectively, by reducing flow index of these spacer fluids, and displacement efficiencies can be enhanced significantly as displacement interface length reduction. At ideal eccentric central degrees, it is necessary to maintain low flow indexes, otherwise severe channeling of cement slurries might be expected. In conclusion, the rheological properties of spacer fluids and eccentric degrees of casing shall be considered during design and implementation of cementation operations to minimize possibility of channeling on wider side of the casing so as to enhance quality of cementation operations.