Abstract: When a subsea production system is used to develop a deep-water gasfield in the South China Sea, the tieback pipeline is long with big elevation difference, so flow safety assurance is the key to successful gasfield development. In this paper, the operation condition of tieback pipeline in gasfield is simulated with OLGA. The simulation results show that when the gasfield production is lower than the minimum capacity of tieback pipeline, the liquid holdup and pressure drop of the pipeline increase quickly, so the capacity of tieback pipeline can be improved by injecting circulation dry gas from platform; when the capacity of tieback pipeline decreases or increases, the process facilities on shallow-water platform will be greatly affected. All possible conditions should be analyzed in the gasfield development, and flow safety assurance technology can provide a guidance to the safe and efficient production of gasfield.