CARBON DIOXIDE INJECTION INTO SHALLOW SEDIMENTARY AQUIFER SYSTEMS TO ASSESS POTENTIAL DEGRADATION OF GROUNDWATER QUALITY AT GEOLOGICAL CARBON SEQUESTRATION SITES

Currently there is little information on impacts of CO₂ leakage on potable groundwater under controlled field conditions. Theoretical modeling studies may not be reliable because of large uncertainties in model parameters such as reaction rate constants. We presented here an integrated method for assessing impacts of CO₂ leakage on groundwater quality based on single well push-pull tests in shallow sedimentary aquifers at a geological carbon sequestration site in the Gulf Coast, laboratory batch experiments and numerical models. The laboratory batch experiments will be conducted with the aquifer sediments and groundwater taken from the target aquifer in a beaker under a controlled CO₂ flushing. The lab experimental results will used to identify geochemical parameters related to mobilization of elements caused by CO₂ injection and provide preliminary information on designing push pull tests in which CO₂ saturated groundwater will be injected into an aquifer and, after a prespecified time, groundwater will be extracted for analyses of major and trace elements and carbon, oxygen, strontium, iron, and lead isotopes. Reactive transport modeling will be conducted to design field tests and to analyze test results. Data from field, laboratory, and modeling analyses will be used to identify key geochemical processes related to groundwater-quality impacts of CO₂ injection (e.g., pH reduction and trace-metal mobilization). The field studies will be conducted in Cranfield, Mississippi, at an existing test site for deep geologic carbon sequestration in a typical Gulf Coast alluvial aquifer. Preliminary results are presented.