Comparative investigation on the heat extraction performance of an enhanced geothermal system with N2O, CO2 and H2O as working fluids

The properties of geothermal working fluids have great influence on the heat extraction performance of an enhanced geothermal system (EGS). In addition to H2O, N2O and CO2 have also been proposed as geothermal working fluids. In order to analyze and compare the heat extraction performances of the N2O, CO2 and H2O EGS, a two-dimensional thermo-hydraulic-mechanical (THM) coupled EGS model with discrete fractures is established. In addition, the influences of injection-production parameters on the heat extraction effects of EGS with different working fluids are also analyzed. The results indicate that the heat extraction performances of N2O-EGS and CO2-EGS are almost the same under the same conditions. Taking into account the stable production time and the stability of supporting equipment, the performances of N2O-EGS and CO2-EGS are better than H2O-EGS. Furthermore, a lower injection temperature is conducive to the heat extractions of N2O-EGS and CO2-EGS, while the injection mass flow rate and production pressure should be designed reasonably according to the actual situation. As for H2O-EGS, a higher production pressure is conducive to its performance, while its injection temperature and injection mass flow rate should be designed reasonably.

Automated summary

The heat extraction performances of N2O-EGS and CO2-EGS are almost the same under the same conditions, and better than H2O-EGS. A lower injection temperature is conducive to the heat extractions of N2O-EGS and CO2-EGS, while the production pressure, injection mass flow rate should be designed reasonably according to the actual situation.