Abstract
CO2 geological storage in deep saline aquifers is an effective way to reduce CO2 emissions. The injection of CO2 inevitably causes a significant pressure increase in reservoirs. When there exist faults which cut through a deep reservoir and shallow aquifer system, there is a risk of the shallow aquifer being impacted by the changes in reservoir hydrodynamic fields. In this paper, a radial model and a 3D model are established by TOUGH2-ECO2N for the reservoir system in the CO2 geological storage demonstration site in the Junggar Basin to analyze the impact of the CO2 injection on the deep reservoir pressure field and the possible influence on the surrounding shallow groundwater sources. According to the results, the influence of CO2 injection on the reservoir pressure field in different periods and different numbers of well is analyzed. The result shows that the number of injection wells has a significant impact on the reservoir pressure field changes. The greater the number of injection wells is, the greater the pressure field changes. However, after the cessation of CO2 injection, the number of injection wells has little impact on the reservoir pressure recovery time. Under the geological conditions of the site and the constant injection pressure, although the CO2 injection has a significant influence on the pressure field in the deep reservoir, the impact on the shallow groundwater source area is minimal and can be neglected and the existing shallow groundwater sources are safe in the given project scenarios.
Highlights
Global warming presents a serious threat to the living environment of humans
Birkholzer et al [17, 20] argued that numerical simulations of large industrial-scale carbon capture and storage (CCS) projects show that pressure changes caused by CO2 injection may spread far within a CO2 reservoir and may even affect the entire reservoir and basin
The CO2 diffusion and reservoir pressure field changes caused by CO2 injection via different numbers of injection wells were analyzed by numerical simulation
Summary
Global warming presents a serious threat to the living environment of humans. Reducing the emissions of carbon dioxide (CO2) is a common challenge for countries worldwide [1]. The geological storage of CO2 has attracted the attention of governments and scientists around the world as a direct and effective emission reduction method recognized by the international community [2,3,4,5]. Suitable storage sites include former gas and oil fields, deep saline formations, or nearly depleted oil fields where the injected carbon dioxide may increase the amount of oil recovered. The geological storage of CO2 is a complex process and is affected by many factors, such as the reservoir conditions, rock heterogeneity, faults, minerals, relative permeability hysteresis, and dip angle of the reservoir[6,7,8,9]. Two important potential risks associated with the pressure increase have attracted the attention of many scholars. The second risk involves environmental impacts, such as the impacts on shallow aquifers and
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