Risk-Based Decision Making for Assessing Potential Impacts of Geologic CO2 Sequestration on Drinking-Water SourcesEPA Grant Number: R834387
Title: Risk-Based Decision Making for Assessing Potential Impacts of Geologic CO2 Sequestration on Drinking-Water Sources
Investigators: McCray, John , Kaszuba, John , Maxwell, Reed , Sitchler, Alexis
Current Investigators: McCray, John , Maxwell, Reed , Sitchler, Alexis
Institution: Colorado School of Mines , University of Wyoming
Current Institution: Colorado School of Mines
EPA Project Officer: Klieforth, Barbara I
Project Period: February 1, 2010 through January 31, 2013 (Extended to January 31, 2014)
Project Amount: $899,987
RFA: Integrated Design, Modeling, and Monitoring of Geologic Sequestration of Anthropogenic Carbon Dioxide to Safeguard Sources of Drinking Water (2009) RFA Text | Recipients Lists
Research Category: Drinking Water , Water
The capture and sequestration of carbon dioxide (CCS) is an important part of any plan to mitigate anthropogenic CO2 emissions. Without CCS it is unlikely that conservation or new technologies will stabilize concentrations of CO2 in the atmosphere at a level that is acceptable, according the IPCC reports. Deep geologic formations are an attractive repository for carbon dioxide due to their ability to naturally store gasses for long periods of time, but it is likely that these formations will leak CO2 into overlying formations, including fresh-water aquifers used to supply domestic drinking water. However, the amount of acceptable leakage and the effects this leakage may have on underground drinking water sources is unknown. The most important impacts of leakage on aquifer water quality have yet to be determined. To assess these impacts, methods to quantify the risk associated with leakage are needed.
The total risk associated with CO2 leakage from deep geologic formations can be broken into two categories: 1) the risk of leakage through the caprock and 2) the risk of decreased aquifer water quality upon introduction of CO2. Methods used in caprock assessement for oil and gas reservoirs are currently being adapted for sequestration purposes by other researchers. The focus of this proposal is to develop a methodology to quantify the susceptibility of an aquifer to contamination from CO2 leakage, and to assess the risk of decreased aquifer quality. Research to rigorously quantify risk of aquifer contamination due to CO2 leakage from deeper sequestration targets has not been previously published.
We propose a combination of laboratory experiments and innovative reactive transport numerical simulation to 1) understand the geochemical reactions between CO2, aquifer fluids, and aquifer minerals that ultimately determine the quality of drinking water sources and 2) quantify the risk associated with leakage of CO2 into potential drinking water sources using a probabilistic approach. We propose a framework for a decision-making tool based on results of the research outlined in this proposal.
Two scenarios of CO2 leakage into potential underground drinking water sources will be investigated if funded, 1) a shallow aquifer where CO2 will be present in the gas phase and 2) a deeper aquifer where CO2 will remain in a supercritical state. The source of CO2 is assumed to be deeper saline aquifer. Numerical modeling will be used to identify parameters such as mineralogy, hydraulic conductivity, pH, and mineral trace metal concentrations, that are likely to increase the susceptibility of an aquifer to contamination upon leakage of CO2. Experiments will be designed to examine how parameters identified in the preliminary modeling contribute to the impact of CO2 on aquifer water quality. The information from the experiments will then be used to inform additional process-based reaction and transport modeling to quantify the impacts on aquifer water quality. From results of these modeling efforts, computationally simpler stream-tube models will be implemented to enable a rigorous probabilistic risk assessment.
Results of this project will provide guidance on what hydrogeochemical factors or parameters are the best measures to identify high-risk aquifers and quantify potential degradations in aquifer water quality. An outcome is a methodology to assess the susceptibility of any aquifer to CO2 leakage using known, or measurable parameters.