Geomechanical analysis of intraplate earthquakes and earthquakes induced during stimulation of low permeability gas reservoirs [electronic resource]

This thesis applies the principals of geomechanics to address a breadth of fundamental scientific questions regarding rock properties near major active faults, physical mechanisms driving intraplate earthquake activity, and how induced earthquakes in low-permeability natural gas reservoirs provide insight into reservoir deformation during hydraulic fracture stimulations. The first part of this thesis applies a shear-wave splitting analysis to examine physical controls on crustal anisotropy mechanisms on and near the North Anatolian Fault in northwest Turkey. The analysis indicates that stress-controlled mechanisms appear to prevail at distances greater than 1 km from the main fault trace while structure-controlled mechanisms are observed within 1 km of the main fault trace, suggesting the existence of heterogeneous physical properties between the main fault zone and surrounding crust. The second part of this thesis applies fundamental geomechanical principals to examine the compatibility of shear slip on intraplate faults in the central and eastern United States and southeastern Canada with frictional faulting theory in the context of the regional tectonic stress field. The application demonstrates that maximum horizontal stress orientations consistently trend NE-SW across the study area, horizontal principal stress magnitudes become increasingly compressive with respect to the vertical stress moving from the central U.S. toward the northeastern U.S. and southeastern Canada, and shear slip on the vast majority of intraplate fault planes is well described by the Mohr-Coulomb failure criterion in the current stress field assuming hydrostatic pore pressure in the upper crust and laboratory-determined coefficients of fault friction. The final part of this thesis applies an integrated, geomechanical and seismological analysis to evaluate the response of low permeability natural gas reservoirs to hydraulic fracturing stimulations in two case studies in western Canada. Geomechanical, waveform similarity, and microseismic event magnitude scaling analyses indicate that the reservoir response to hydraulic fracturing is generally characterized by shear deformation occurring on small faults reactivated during hydraulic fracturing stimulations. The advanced double-difference earthquake relocation technique is applied to improve microseismic event hypocenter locations. While the technique reduces scatter in microseismic event hypocenter locations, it is susceptible to producing hypocenter location artifacts in limited (single or double) monitoring array configurations. However, synthetic test show the double-difference technique could be a viable tool in accurately relocating microseismic events provided a suitable monitoring array configuration (three arrays or more) exists.

Keywords: Geophysics
Advisor: Zoback Mark D. primary advisor. Thesis advisor
Beroza Gregory C. (Gregory Christian) advisor. Thesis advisor
Kovscek Anthony R. (Anthony Robert) advisor. Thesis advisor
Sleep Norman H. advisor. Thesis advisor