Petrographic, mineralogical, and geochemical evidence of diagenesis in the Eau Claire formation, Illinois basin: Implications for sealing capability in a carbon dioxide sequestration system
Abstract
Amid growing concerns of anthropogenically induced climate change, researchers across the world are working to assess the viability of geological storage of carbon dioxide (CO2). In the Illinois Basin, the Mount Simon Sandstone, a deep saline aquifer, has been targeted as a reservoir for carbon capture and storage (CCS). In this CCS system, the Eau Claire formation is expected to serve as the primary seal to prevent upward migration of the CO 2 plume. As the Eau Claire Formation has been of little economic importance in the past and exists entirely in the subsurface in the Illinois Basin, little work has been done on this unit to determine how it will perform as a seal, and most of this work is geophysical log based. The lateral extent and thickness of this unit certainly make it amenable to serving in this capacity; however, the primary depositional fabric and mineralogy to this point are still poorly constrained. These factors are examined in depth in this study by utilizing petrography, reflectance spectroscopy, x-ray diffraction, and geochemical analysis on core derived samples from seven wells that span the Illinois Basin. These analysis show the Eau Claire Formation is quite heterogeneous with respect to both fabric and mineralogy. Available porosity and permeability data suggest that presently the Eau Claire Formation should have the capability to serve as a suitable seal. However, the unit does contain a mineral suite that has the potential to prove quite reactive with a CO2 rich brine. These minerals include dolomite, ankerite, calcite, glauconite, chlorite, and to a lesser degree feldspars. Many minerals within the Eau Claire Formation are authigenic in nature, and it is also apparent that some minerals have been selectively dissolved. This indicates that there have been multiple generations of fluid systems in the Eau Claire Formation. Future dissolution of the reactive minerals may pose a threat to the sealing integrity of the Eau Claire Formation, though the dynamics of the CCS system along with precipitation of new minerals and choking of pore throats should allow the unit to serve as an adequate seal.
Degree
M.S.
Advisors
Bowen, Purdue University.
Subject Area
Geology|Climate Change|Sedimentary Geology
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