Short-term safety risk assessment of CO₂ geological storage projects in deep saline aquifers using the Shenhua CCS Demonstration Project as a case study

Although CO₂ geological storage has been recognized as an effective strategy to lower carbon emissions directly, there are no suitable guidelines for safety risk assessment of CO₂ geological storage projects in deep saline aquifers in China and elsewhere. When CO₂ is injected into deep saline aquifers, stratigraphic and structural trapping is the major basic mechanism controlling CO₂ storage capacity and migration in reservoirs. Therefore, a safety risk assessment method is proposed in this paper using perspectives from hydrogeological and environmental geology. The uncertainties and risks consist of CO₂ leakage, ground deformation, and induced earthquakes. Identifying and assessing potential risks are the first and most important step in the process of risk assessment. Based on the identification of risks of CO₂ geological storage projects, we built an elementary risk evaluation index system in an analytic hierarchy process framework. Meanwhile, the possibility of occurrence and damage to the environment and public caused by CO₂ leakage, ground deformation, and induced earthquakes was analyzed in detail, and current risk criteria were also summarized. Furthermore, using the Shenhua CO₂ Capture and Storage Demonstration Project as a case study, we performed a risk identification and evaluation by using qualitative or semi-quantitative methods in sequence, as well as developing the related preliminary risk management measures. This method and case study for short-term safety risk assessment could provide a guideline for site selection, injection design, and monitoring of CO₂ geological storage projects in deep saline aquifers.