An integrated system of CO2 geological sequestration and aquifer thermal energy storage: Storage characteristics and applicability analysis

The carbon dioxide (CO2) 2 ) geological storage is an effective technology for the carbon emission reduction, but the high-priced sequestration has become the main factor restricting the development. Meanwhile, surface waste heats are difficult to be effectively utilized, and energy supply and demand have been unbalanced for a long time. In order to solve the above problems, this study proposed an integrated system in accordance with the concept of the carbon capture, utilization and storage (CCUS) technology, realizing the aquifer storage of heats and CO2 2 at the same time. Based on the numerical model considering the gas-water dissolution, CO2 2 saturation distributions, temperature distributions and well performances of the integrated system were analyzed. The CO2 2 storage performance and heat extraction performance of the integrated system were quantitatively evaluated. Furthermore, economic performances and applicabilities of closed-loop and open-loop systems were compared and discussed. The results show that variations of CO2 2 solubility and physical properties constitute a complex coupling process between the heat storage and CO2 2 sequestration in the integrated system. The CO2 2 migration radius during the high-temperature injection is reduced by 13 % compared with the case without considering the heat storage. In an underground space of approximately 5.76 x 108 8 m3, 3 , CO2 2 storage capacities of closed-loop and open-loop systems during the injection period are 11.935 Mt and 5.741 Mt with effective storage ratios of 97.5% and 93.2 %, respectively. The open-loop system enhances the carbon sequestration ability of the integrated system because of a fewer proportion of free gas. Thermal performances of the closed-loop system are much weaker than that of the open-loop system, thus showcasing a poor heat extraction economic performance. After 20 years, closed and open systems can offset part of CO2 2 storage costs with $4998.8 and $576973.5, respectively. According to outlet temperature differences, the closed-loop system can be used for the high temperature reservoir reconstruction and the district heating with the main purpose of CO2 2 storage, while the open-loop system is suitable for the seasonal underground heat storage, central heating system and even geothermal power generation with the main purpose of CO2 2 utilization. This study provides a new path for the carbon capture, utilization and storage technology.