Carbon Sequestration in Deep Saline Aquifers

Lab technicians Shane Butler and Lois Yolksoulian work on the project from a lab in the Natural Resources Building. The first annual project report was submitted to the U.S. Environmental Protection Agency in fulfillment of the 3-year project "Protecting Drinking Water by Reducing Uncertainties Associated with Geologic Carbon Sequestration in Deep Saline Aquifers." Project members include personnel from the Illinois State Geological Survey (ISGS), Illinois State Water Survey, Stanford University, and the University of Hawaii.

During the first year, a quality assurance project plan was created with input from all the investigators, submitted, and approved. Staff began meeting with the gas storage companies to review their data.

A geological model of the Illinois Basin Pilot Project was developed using data provided in the open literature. Based on this model, the ISGS performed simulations using the computer code TOUGH2 to predict the pressure buildup at an observation well located about 300 m from the injection well. The regional groundwater model (MODFLOW) was significantly improved by increasing the horizontal spatial resolution in northeastern Illinois, increasing the vertical spatial resolution at regional scale, and increasing the saturation stability of the groundwater flow model at the Ironton-Galesville aquifer on top of the Mt. Simon Sandstone.

Preliminary geochemical experiments were conducted with pressure vessels and core samples of the Mt. Simon Sandstone collected from the Illinois Basin-Decatur Project. A protocol was developed for safely pressurizing the reaction vessels with carbon dioxide using an air-driven, pneumatic pump. Experience was gained in assembling the pressure vessels after adding rock samples and a synthetic brine, and simultaneously heating and pressurizing the vessels to pressures and temperatures corresponding to injection formation conditions. A detailed core sampling and analysis plan was also created to ensure that sufficient sample would be available for each experiment and for chemical and mineralogical characterization.

Results showed that the saline springs of the Illinois Basin are coincident with geologic structures (faults, folds) within the Basin and coincident with the Basin margins. Formations of origin have been identified for most of the samples where halide data are available, and the ISGS should be able to identify, with reasonable certainty, the origin of all saline spring waters in the Illinois Basin.