Geomechanical Assessment of Induced Seismicity During CO2 Injection in Illinois Basin
Abstract: Injection of carbon dioxide (CO2) into deep underground formations is a promising approach to mitigate accelerating greenhouse gas emissions. However, it affects the state of stress in the subsurface, potentially making it more favorable for fault reactivation and earthquakes. The injection process is associated with complex hydromechanical behavior which cannot be accurately characterized solely based on geophysical data, highlighting the need for precise laboratory testing. Additionally, induced seismic response is usually associated with three-dimensional features, such as local stratigraphy, fractures, faults, and discontinuities rather than failure of intact rock. Simplification or neglecting these features might introduce additional bias in the assessment, while their accurate representation requires millions of grid points in the numerical domain
In this presentation, the results of laboratory testing are combined with high-performance numerical modeling to assess the risk of induced seismic response during CO2 injection at IBDP site in Illinois Basin. Set of material properties required for consideration of coupled hydromechanical response are measured in the laboratory experiments for reservoir (Mt. Simon sandstone), basal sealing (Argenta sandstone), and intact and fractured crystalline basement (Precambrian rhyolite) formations. The conducted experiments address strength, poromechanical response, single- and two-phase permeability of tight rock specimens at representative conditions. High-resolution numerical modeling allows to consider the stratigraphy of injection site and reconstruct three-dimensional state of stress and its evolution during the injection. Results suggest that clusters of microseismicity observed in the crystalline basement during the injection are associated with critically stressed zones that are formed due to the local stratigraphy of the site and reactivated during the injection. Finally, the recommendations for assessing future CO2 injection projects are formulated, drawing insights from the pilot-scale project in the Illinois Basin. These suggestions include the need for more advanced constitutive models, supplementary stress measurements, and consideration of geologic formations’ heterogeneities
