Monitoring, verification, accounting (MVA), and defining lowermost underground sources of drinking water (USDW) at a deep saline, carbon sequestration site

Geologic carbon sequestration involves the injection of carbon dioxide (CO2) into suitable saline reservoirs such as the Mt. Simon Sandstone located in the Illinois Basin. A Monitoring, Verification, and Accounting (MVA) program for a Carbon Capture and Storage (CCS) project involves methods to monitor for CO2 leakage from the injection reservoir, verification of the monitoring data and accounting for the amount of CO2 leaked. The USDOE has funded a demonstration project for the capture and storage of CO2 from the Archer Daniel Midland ethanol plant in Decatur, Illinois. This project will test the ability of the Mt. Simon sandstone to store CO2 within the brine saturated formation. Over a three-year period, one million tons of CO2 will be injected into this sandstone at a depth of approximately 6,500 feet. The MVA program will examine the effectiveness of long-term storage of CO2 in the Mt. Simon by monitoring the injection reservoir and formations immediately above the caprock using seismic imaging and pressure and fluid sampling. The shallower geologic environment such as groundwater, vadose zone soil-gas, and atmospheric CO2 fluxes will also be monitored. This monitoring will take place before, during, and after CO2 injection to provide data that will be verified by modeling efforts to determine if CO2 leakage is occurring. This information will also be used to determine what monitoring tools will be cost-effective for commercial-scale CCS projects. As part of ADM's injection permit, the Illinois EPA requires that the water quality of the lowermost underground source of drinking water (USDW) be monitored. A monitoring well will be drilled to a depth of 800 feet because geophysical logs from local wells indicate that groundwater exceeds the 10,000 mg/L total dissolved solids standard at this depth. Several methods (borehole logging, packer testing, and groundwater sampling) will be used to identify the lowermost USDW at this site.