Abstract
Our previous study (Chang and Segall, J Geophys Res Solid Earth 121(4):2708–2726, 2016a) demonstrated that diffusion of pore-pressure and stress into basement rocks can cause slip on deep faults, potentially inducing seismicity. Recent studies suggest that the presence of a bottom-sealing layer between the injection horizon and basement will reduce the magnitude of injection-induced pore-pressure in the basement due to contrasts in permeability and/or storage capacity. In this study, we examine the role of basal sealing horizons in induced seismicity on basement faults by adding a layer beneath the reservoir into the two-dimensional, fully coupled poroelastic model developed previously. We consider two types of basal seals: (1) a low-permeability seal and (2) a high-storativity seal. The analysis of the spatio-temporal change in Coulomb stress and time-dependent rate of earthquake nucleation confirms that both types of seal inhibit direct pore-pressure diffusion into basement rocks, but poroelastic stresses are still transmitted, potentially inducing earthquakes. The high-storativity seal reduces the transmission of poroelastic stresses into the basement, minimizing seismicity on basement faults in comparison to the low-permeability seal.
Published Version
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