Risk assessment addresses the effects, positive or negative, of uncertainty on objectives and considers the probability and impact of unfortunate events. Risks are managed by identifying, assessing, and prioritizing them, then applying resources to minimize, monitor, and control them or maximize the realization of associated opportunities. As an integral part of risk management planning, risk assessment involves the study of the probability, impact, and effect of known risks on a project and the corrective action to take if a risk occurs. An objective evaluation of risk requires careful consideration and presentation of underlying assumptions and uncertainties.
PNNL geoscientists are collaborating with other national laboratories through the U.S. Department of Energy’s National Risk Assessment Partnership (NRAP) on targeted research to provide science-based methodologies to evaluate and mitigate potential risks associated with long-term storage of carbon dioxide (CO2) in geologic formations, saline aquifers, depleted oil and natural gas reservoirs, and basalt reservoirs. Through NRAP, PNNL is leading multi-laboratory research teams that are assessing CO2 leakage via natural pathways such as fractures and faults in geologic reservoirs and caprock, understanding corrosion and subsequent leakage through wellbore cements and casings, predicting impacts on groundwater if reservoir leakage occurs, and developing innovative monitoring techniques for plume inventory and leakage assessment. This research will provide a robust, defensible, science-based approach for quantifying risk associated with long-term CO2 storage.
Risk Assessment Team: This team is developing the scientific basis for a risk assessment model to address risk associated with long-term storage of CO2. The team will study mineralogical and geochemical changes produced by rock-brine-CO2 reactions within geologic reservoirs and overlying caprocks; determine likely geochemical reactions that control dissolved contaminant concentrations and their fate; and assess the impact of these reaction mechanisms on long-term risk profiles for geologic carbon sequestration projects.
Natural Leakage Pathways Team: This team is researching how to better predict the performance of caprocks covering carbon sequestration geologic reservoirs, and the potential for supercritical CO2 leakage through faults and fractures. They are using data from three-dimensional numerical models to help quantify the amount of CO2 leakage, potential pathways, and absorption into the caprock. Scientists are exploring various caprock factors, including how the type, strength, and thickness of a caprock can effectively resist CO2 leakage. For example, marine shale caprock usually has low permeability and would naturally resist CO2 leakage if it is more than 10 to 20 meters thick.
Groundwater Team: Injection of CO2 into geologic reservoirs can result in significant geomechanical stresses to the reservoir, caprock seals, faults and fractures, and wellbores in the region. These stresses can cause CO2 and brine leakage, which can potentially impact groundwater and surface water. This team is studying long-term effects of CO2 leakage and how to protect natural water resources by using laboratory and computational tools to understand the impact of CO2 and brine leakage on groundwater chemistry.