Wellblock W in Weizhou oilfield A is developed with dry gas injection, which results in increased pressure and production after gas injection.However, the production performance in recent years shows that there is well fluid accumulation in gas injection well and uneven production degree of each sand body,which restricts the development of gas injection.Based on the phase equilibrium theory and thermodynamic equilibrium theory,the accurate fluid composition and phase state model can be obtained by multiple fluid recovery, flash and parameter fitting based on the difference of fluid composition and characteristics in longitudinal direction.The relationship between the fluid dew-point pressure and gas-oil ratio with the proportion of equilibrium oil added after restoration is analyzed.Through the addition of equilibrium oil and the phase diagram, the fluid phase state of injected gas under formation conditions is analyzed,thus the real phase change of injected gas with the change of temperature and pressure is obtained,which provides a favorable basis for the analysis of bottom hole fluid accumulation in the gas injection well.After considering the injection cost and workover cost, it is proposed that the injection should be cleaned first, and then the injection gas component should be changed to remove the fluid accumulation in the wellbore,effectively improve the suction profile of each sand body, and increase the recovery rate of the block by 1.3%.The results have a guiding role in the determination of fluid phase state, dynamic analysis and optimization of development plan of gas injection development.