Abstract: Hydrate is formed in the wells of the gas injectors for natural-gas gravity miscible flooding in Pubei Oilfield, which seriously impacts the gas injection efficiency of the gas injectors. The pipe sections with hydrate and the influence factors were analyzed based on Pipesim modeling, and the technical feasibility of increasing the initial temperature of natural gas and heating the wellhead natural gas by using a water jacket heater to prevent the formation of hydrate was researched. It is indicated that under current gas injection conditions, there are suitable temperature and pressure conditions for the formation of hydrate in the gas pipeline 300-2 000 m away from the compressor outlet and in the well above the depth of 1 025 m. With the increase of initial natural gas temperature and gas injection rate, when the wellhead gas temperature is lower than the highest temperature for the formation of corresponding hydrate, the gas pipeline section with hydrate gets shorter and the hole section with hydrate gets longer first and then shorter; and when the wellhead gas temperature is higher than the highest temperature for the formation of corresponding hydrate, no hydrate is formed in the gas pipeline and the well section with hydrate gets shorter. What’s more, increasing the initial temperature of natural gas and heating the wellhead natural gas by using a water jacket heater can prevent the formation of hydrate in the gas injectors with gas injection pressure less than 40 MPa and gas injection rate more than 5×10⁴ m³/d, so it is an effective hydrate prevention method.