Abstract: To address the problem that hydrate generation is prone to blocking wellbores and production pipes in the development of sour natural gas reservoirs, the hydrate formation conditions were experimentally determined with constant-temperature pressure search method for gas samples taken from two natural gas reservoirs with high CO₂ content in Western China. It was found in the study that high CO₂ content in natural gas increased the HCO₃^- ion content of formation water, thereby improving the salinity of formation water; compared with pure CH₄ gas, the existing CO₂ significantly reduced the formation pressure required for gas hydrate generation under the same temperature conditions compared with pure CH₄ gas. For the target gas fluid, there was no obvious difference in hydrate formation conditions between low-salinity formation water and pure water; the pressure of gas hydrate formation in formation water with high salinity (16 970.7 mg/L) was significantly higher than that in pure water system. Further, the decomposition enthalpy of the synthesized hydrate was calculated based on the Clausius-Clapeyron equation as 62 kJ/mol, and the gas hydrate formed was of Type I structure. Finally, the characteristics of hydrate formation in the target gas reservoir development process were analyzed in combination with experimental data and production performance data, and the hydrate formation in the wellbore and the location of the wellbore where the hydrate formed were predicted. There is much for reference of the results of the study to the prevention of hydrate formation in field production.

Key words: hydrate, sour natural gas, high CO₂ content, formation conditions, hydrate blockage, formation water