| Title | An experimental investigation of feasibility of supercritical CO2 geothermal heat mining in low and medium temperature geothermal reservoir |
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| Authors | Shidong Li, Jianwen Dai, Mingying Xie, Shasha Feng, Yujin Huang, Nanji Hadia, HonChung Lau, Ludger Stubbs |
| Year | 2023 |
| Conference | World Geothermal Congress |
| Keywords | Supercritical CO2; low and medium temperature geothermal reservoirs; heat map; |
| Abstract | The global warming caused by CO2 emission has drawn worldwide attention, and many countries have committed to achieve carbon neutral around middle of 21st century. Using supercritical CO2 as a heat carrying fluid to produce geothermal resources may be a promising potential to CO2 emission, because it can generate green energy (electricity and direct heating) and store massive amount of CO2 simultaneously. Since low and medium temperature geothermal reservoirs have wider distribution, hence applying abovementioned technology to these reservoirs may have more significate effect on CO2 sequestration. The objective of this paper is to investigate the feasibility of using supercritical CO2 for heat mining for low and medium temperature geothermal reservoirs. In this study, we built a large scale high pressure sandpack experimental setup with 83 thermal couples and a heat exchanger to conduct supercritical CO2 heat mining experiments. The sandpack was preheated to a given temperature at certain pressure, then liquid CO2 was injected into the sandpack with a certain flow rate for several pore volumes. The temperature distribution inside the sandpack was measured with thermal couples in real-time, as well as the temperature of inlet, outlet and heat exchanger. Different temperatures (80℃, 100℃ and 120℃), pressure (80bar, 100bar and 120bar) and flow rates (25ml/min, 50ml/min and 100ml/min) were utilized to study the heat mining performance of supercritical CO2 under different conditions. The heat mining experiments were conducted also for water with the same conditions to compare the performance. The experimental results can plot the heat map of the sandpack at different pore volumes and reveal the heat transfer mechanism during supercritical CO2 injection. The heat exchanger is sufficient to compare the performance of different injection scenario. The injection with higher temperature, pressure and flow rate generate better heat mining performance and achieved higher temperature in heat exchanger. Supercritical CO2 is a good heat carrying fluid for heat mining, even though it has less heat capacity but lower viscosity allows it can be injected with high flow rate. This lead to better heat mining performance than water in low and medium temperature geothermal reservoirs. |