Geomechanics of injection-induced seismicity in Illinois Basin
Advisor: Professor Roman Makhnenko
Virtual location: https://illinois.zoom.us/j/86063475670?pwd=UU1KZW9PbnFaeGgveXJaU3FRSXdKdz09
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 dissertation, field observations, laboratory experiments, and numerical modeling are combined within self-consistent framework to improve risk assessment related the induced seismic response that occurred during the CO2 injection for Illinois Basin Decatur Project (IBDP). Set hydromechanical properties response is measured 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 and heterogeneity 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.
