Relationship between microseismicity and high pore pressures during hydraulic stimulation experiments in low permeability granitic rocks
Several hundred microearthquakes with local magnitudes ranging between -4 and -2 were recorded during hydraulic stimulation experiments at the hot dry rock demonstration site, Fenton Hill, New Mexico. These events are probably caused by shear failure induced by high pore fluid pressures. Since the event locations seem to cluster in a narrow band near the hydraulic fracture, we were able to use microseismic techniques to locate the hydraulic fracture and monitor its growth. We calculate the minimum pore pressure increase necessary to induce rock failure using a simple model of slippage on preexisting fractures. By comparing a pore pressure distribution, calculated using a one-dimensional diffusion model with the distribution of event foci, we demonstrate that high pore pressures are a probable cause for these microearthquakes. Stress drops for these microearthquakes, calculated from spectral parameters, increased by a factor of 3 during the course of the experiment. The stress drop increase correlates with a migration of seismic activity away from the injection well bore, which suggests relatively low in situ shear stresses near the well bore caused by strain release in this region during previous pressurizations.
- Research Organization:
- Los Alamos National Lab., NM
- OSTI ID:
- 6372557
- Journal Information:
- J. Geophys. Res.; (United States), Vol. 86:B9
- Country of Publication:
- United States
- Language:
- English
Similar Records
Hot dry rock fracture propagation and reservoir characterization
Stress control of seismicity patterns observed during hydraulic fracturing experiments at the Fenton Hill hot dry rock geothermal energy site, New Mexico
Related Subjects
15 GEOTHERMAL ENERGY
GEOTHERMAL WELLS
HYDRAULIC FRACTURING
HOT-DRY-ROCK SYSTEMS
MICROEARTHQUAKES
ACOUSTIC MONITORING
GRANITES
NEW MEXICO
POROSITY
PRESSURE DEPENDENCE
SEISMIC NOISE
COMMINUTION
EARTHQUAKES
ENERGY SYSTEMS
FEDERAL REGION VI
FRACTURING
GEOTHERMAL SYSTEMS
IGNEOUS ROCKS
MONITORING
NOISE
NORTH AMERICA
PLUTONIC ROCKS
ROCKS
SEISMIC EVENTS
USA
WELLS
580202* - Geophysics- Volcanology- (1980-1989)
150906 - Geothermal Engineering- Reservoir Stimulation & Extraction Technology
580300 - Mineralogy
Petrology
& Rock Mechanics- (-1989)