地质科技通报 (May 2024)
Safety analysis of geothermal water recharge coupled with CO2 geological storage system
Abstract
Objective In well-trapped hydrothermal geothermal reservoirs, the research on injecting CO2 into reservoirs simultaneously with recharge water is carried out, which has both economic and environmental benefits for carbon sequestration. Methods A 3D reservoir model was established to study the CO2 breakthrough time and the migration of CO2-rich brine in a reservoir under different well spacings, formation inclination angles, sieve tube positions and exploitation and reinjection rates. Results The results show that (1) when the exploitation and reinjection rate is 20 kg/s and the well spacing is 1 200 m within 20 years of operation, there is no CO2 breakthrough. (2) In inclined formations, when the recharge well is located downstream of the production well, as the formation inclination angle increases, the CO2 breakthrough time increases, and the migration distance of carbonated water increases along the downdip direction of the formation. (3) Considering the impact of the screen position on the breakthrough time and CO2 mass fraction in the production well after breakthrough, it is beneficial to ensure the safety and effectiveness of CO2 geological storage when the recharge well sieve tube is located 30 m above the reservoir and the production well sieve is located 30 m below the reservoir. (4) The exploitation and reinjection rates have greater impacts on the CO2 breakthrough time. When the exploitation and reinjection rate is 12 kg/s, there is no CO2 breakthrough. When the exploitation and reinjection rate increases to 28 kg/s, the breakthrough time decreases to 11.8 years. Conclusion Therefore, in practical engineering applications, the CO2 breakthrough time can be delayed, and the safety of CO2 geological storage can be improved through the study of operating parameters and the inherent characteristics of the formation.
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