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Título del libro: 55th U.S. Rock Mechanics / Geomechanics Symposium 2021
Título del capítulo: Combining Microseismic Observations and Reservoir Simulation to Interpret Fracture Criticality in Faults at the Hellisheiði Geothermal Field, Iceland

Autores UNAM:
VALA HJORLEIFSDOTTIR;
Autores externos:

Idioma:

Año de publicación:
2021
Palabras clave:

Critical current density (superconductivity); Criticality (nuclear fission); Geothermal fields; Induced Seismicity; Pore pressure; Probability distributions; Rock mechanics; Fault reactivation; Fault zone; Fluid injections; Geothermal power generation; Icelands; Microseismicity; Potential threats; Pressure change; Reservoir-simulation; Seismic risk; Fracture


Resumen:

Fault reactivation and associated microseismicity induced by fluid injection into the subsurface pose a potential threat in geothermal power generation. In this research, the gradient of critical pore pressure change to trigger seismicity ( pc/h), referred to as the fracture criticality, has been proposed to represent the critical state of subsurface fractures. The fracture criticality is subjected to variability due to heterogeneous fracture attributes and rock properties. The statistics of fracture criticality could be applied to the probabilistic evaluation of fluid injection-induced seismic risk, which considers the injection-driven pore pressure increase, the variability of fracture criticality, and local fracture density. The seismic risk evaluation based on statistics of fracture criticality was applied to the Hellisheiði geothermal site, where microseismic observations and reservoir simulation over a half-year fluid injection period were integrated to achieve the probabilistic distribution of fracture criticality and evaluate the injection-induced seismic risk in both fault and off-fault zones. It has been found that the fracture criticality within both fault and off-fault zones shows natural variability (mostly ranging between 0-1.0 bar/km), and the values estimated roughly follow Gaussian distributions. Relatively high probability of seismic event occurrence was estimated for fault zones around five geothermal fluid re-injection wells at the site, which were consistent with seismically-active areas over the microseismic monitoring period. © 2021 ARMA, American Rock Mechanics Association.


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