Significant progress was made at all three carbon sequestration sites this month, as part of the Midwest Geological Sequestration Consortium Project, Phase II. The final carbon dioxide (CO2) injection well and a deep monitor well at the coal site in Wabash County were drilled, cored, logged, and cased this month. Springfield Coal core samples from the new injection well were placed in desorption canisters depending on maceral type. Springfield Coal core from the second well was preserved for use in a display. In June the wells were perforated, coal permeability was measured with water injection pressure transient tests, and the wells were logged with Schlumberger's cased hole resistivity tool. The CO2 injection is expected to commence in late June. Water and gas samples were also collected from the enhanced coal bed methane pilot.
A groundwater monitoring well was installed at the Archer Daniel Midland plant, Decatur, Illinois. This well will be used in the monitoring, mitigation, and verification (MMV) program for the deep saline reservoir pilot that is part of the U.S. Department of Energy-funded Phase III CO2 geologic sequestration program. The 200-foot-deep well was drilled close to the proposed CO2 injection well to provide geologic information needed to plan the drilling of the injection well. The monitoring well was installed in limestone bedrock and will provide groundwater quality data that will be used in the UIC permit application that requires monitoring of the lowest underground source of drinking water at the site. The well will be developed, and groundwater samples will be collected in the near future.
Illinois State Geological Survey geochemists continue to model the groundwater and brine water quality data collected from the enhanced oil recovery huff-n-puff pilot located in the Louden oil field near St. Elmo, Illinois, the third CO2 sequestration site. The chemical composition of the brine samples continue to change since the termination of CO2 injection. The acidity of the solutions is still increasing. The concentrations of iron, manganese, and potassium initially increased in brine samples collected from the CO2 injection well and are now decreasing. The possible effect of sorption/desorption reactions on the fluid composition are being modeled. The effects of sorption reactions can play an important role in determining fluid composition and, because of the relatively rapid kinetics, are likely to be one of the first aspects of fluid chemistry affected by the introduction of CO2. Sorption onto hematite, possibly available in the subsurface as a cement or grain coating, can be used to explain the decrease in sulfur and the increase in manganese concentration after the introduction of CO2. The change in concentrations is a reflection of the decrease in pH caused by the introduction of the acidic gas. As the pH decreases, the suite of ions that is preferentially on the hematite surface shifts. There is also some dissolution of iron into solution, but these predicted values need to increase more for the model to match the field data.