Numerical simulation of operating parameters of CO₂ plume geothermal system in high temperature gas field

Aiming at the extraction of geothermal resources from high-temperature waste gas reservoirs, the article takes a high-temperature gas field as the target thermal storage, establishes a well-storage fully coupled model with CO₂ as the working fluid through COMSOL software, analyses the thermosiphon effect, changes the CO₂ circulation rate and the diameter of the wellbore respectively, and observes the pressure changes in the injection wells and the production wells, as well as researches the influence of the system operation parameters on the performance of the heat extraction. The study shows that the CO₂ circulation rate has a significant effect on the thermosiphon effect, with smaller wellbore diameters producing a stronger thermosiphon effect. Higher injection temperatures result in a slow decline in the temperature of the production fluid in the later stages of system operation, along with a lower rate of system heat recovery. Larger injection flow rate leads to a rapid decrease in the temperature of the producing fluid. Larger injection and extraction well spacing reduces the fluctuation amplitude of the temperature of the producing fluid and increases the time of the stabilisation phase of the heat recovery rate. The study provides reference significance for the future CO₂-plume geothermal system to carry out deep geothermal energy extraction.