Stratigraphy-Induced Localization of Microseismicity During CO2 Injection in Illinois Basin

Abstract

Subsurface fluid injection stimulates complex hydromechanical interaction, necessitating the integration of geomechanical data across spatial and temporal scales to consider the sophisticated behavior. The induced seismic response is usually associated with reservoir architecture and pre-existing features that are three-dimensional, such as local stratigraphy, fractures, faults, and discontinuities. This study encompasses laboratory characterization of coupled hydromechanical response of rock cores extracted from reservoir - Mt. Simon sandstone, basal seal - Argenta sandstone, and crystalline basement - Precambrian rhyolite - formations in the Illinois Basin. High-resolution numerical modeling allows to consider the three-dimensional complexity of the injection site for Illinois Basin Decatur Project with spatial resolution comparable to one of the active seismic surveys. The laboratory-based porosity-permeability relation is combined with a three-dimensional porosity distribution developed from an inversion of active seismic data resulting in a detailed reconstruction of the evolution of the state of stress in formations where stress measurements are not performed. It appears that the microseismic clusters, mainly observed in the crystalline basement during the injection, are linked to zones experiencing more critically stressed conditions prior to injection. These zones have a potential for reactivation during the injection and are attributed to the specific local stratigraphy of the injection site, as well as transfer of triggering perturbations during the injection.