Induced seismicity potential of the San Juan Basin CarbonSAFE deep
saline carbon sequestration project based on probabilistic geomechanics
Abstract
Although carbon sequestration projects have yet to induce – or may
never induce – a damaging earthquake, experiences from other deep
injection industries such as hydraulic fracturing, enhanced geothermal
systems, and saltwater disposal suggest that effective quantitative
seismic risk assessment is appropriate for deep saline carbon
sequestration (CCS) projects. One such imminent CCS project is the San
Juan Basin CarbonSAFE Phase III program. The study detailed in this
paper utilizes probabilistic geomechanical analyses combined with
observations of the geological and operational parameters of the San
Juan Basin to show that this project is of low induced seismic risk. The
primary analysis is split into four sections. First, we assessed the
literature for faults and past seismicity, and at least five faulting
scenarios are directly relevant. Second, we developed and calibrated a
mechanical earth model for the project site. Third, we performed Monte
Carlo simulations considering reasonable uncertainties of the
geomechanical parameters. Only the Hogback flexural faulting scenario
presented high Coulomb failure functions, but fourth, we determined the
risk to be low based on the combined lack of historical seismicity,
geological framework of the flexural faults, and the presence of
saltwater injection at the same depth as the proposed supercritical
carbon dioxide injection. In order to assess the likelihood of inducing
slip on the basement faults, an analytical treatment of the poroelastic
stress perturbations from the proposed injection was considered, and
this also suggested a low chance for triggering or inducing earthquakes
at this depth. The most sensitive parameters in the geomechanical
calculations were the dip and the coefficient of friction. The least
sensitive were the strike and the orientation of the maximum horizontal
principal stress. In summary, results of this study suggest that the San
Juan Basin CarbonSAFE project is unlikely to induce a medium- or
large-scale event.