--> Evaluation of Potential Geochemical Reactions and Changes in Hydrologic Properties at the Kemper County CO2 Storage Complex

AAPG ACE 2018

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Evaluation of Potential Geochemical Reactions and Changes in Hydrologic Properties at the Kemper County CO2 Storage Complex

Abstract

Following CO2 injection, CO2-brine-mineral interactions may result in mineral dissolution and precipitation reactions that impact rock properties including porosity, permeability, and pore connectivity. The extent and timescale of these alterations largely depends on the reservoir rock properties including the nature and distribution of reactive mineral interfaces. In this work, the potential rate and extent of geochemical reactions and changes in hydrologic properties at the CO2 Storage Complex in Kemper County, Mississippi, USA (Project ECO2S) is evaluated. At this site, the Lower Tuscaloosa, Washita-Fredericksburg, and Paluxy formations have been identified as future regionally extensive and attractive CO2 storage reservoirs. Here, a suite of complementary analyses including powder X-ray Diffraction (XRD) and 2D scanning electron microscopy (SEM) backscattered electron (BSE) and energy dispersive x-ray spectroscopy (EDS) imaging is used in combination with reactive transport simulations to evaluate potential geochemical reactions and changes in formation properties following CO2 injection. Formation samples obtained from potential injection and monitoring wells at the site are evaluated and compared with analyses of regional samples of the formations obtained from the Geological Survey of Alabama. Mineral compositions, determined using petrography and XRD, are used to develop continuum-scale reactive transport simulations to identify potential CO2-brine-mineral interactions with a focus on identifying potential reactive minerals and the corresponding rate and extent of reactions. Mineral reaction rates and changes in the pore structure, including pore connectivity, porosity, and permeability, depend on the spatial distribution and accessibility of minerals to reactive fluids. Spatial maps of mineral distribution will be created using 2D SEM imaging and used to evaluate the nature of the pore-mineral interface, the distribution and accessibility of reactive minerals, and the potential for flow-path modifications resulting from mineral dissolution reactions following CO2 injection. The “Establishing an Early CO2 Storage Complex in Kemper, MS” project is funded by the U.S. Department of Energy’s National Energy Technology Laboratory and cost-sharing partners.