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Title: Acoustic emissions during hydraulic fracturing in granite

Abstract

Hydraulic stimulation experiments being conducted in low-permeability crystalline rocks, at the Department of Energy's Hot Dry Rock Geothermal Site, Fenton Hill, New Mexico, often produce large numbers of microearthquakes. Typically, the early stages of these experiments are aseismic. The rate of acoustic emissions increases rapidly after a critical volume of water, equal to roughly two-thirds of the total amount previously injected, is exceeded, possibly indicating the onset of fracture extension. With local magnitudes ranging between -1 and -6, these events occurring at 3-km depth are too small to detect using surface seismometers, so we monitor the activity using a downhole triaxial geophone system(s) positioned in well(s) close to the reservoir volume. The system provided enough data in early experiments to locate the events using single station seismometry. Recently it became possible to station a second geophone system in a nearby well, that provides valuable additional constraints on event locations. The second tool was also used to measure relative changes in attenuation by comparing signal frequencies for the same event recorded on the two tools. P-wave attenuation does not vary significantly with the source region of the event, however, S-wave attenuation is quite variable, with Q ranging from 170 to 40.more » This suggests that the attenuation may be due to open water-filled fractures. We located large numbers of acoustic events during three hydraulic stimulation experiments, two of which occurred in March 1979 and one in December 1980. During the first two, event locations clustered near a single north-by-northwest trending vertical plane. During the third experiment (after an extended period of heat extraction) the same general trend was evident, but the zone was much wider and events seemed to occur on a series of parallel planes indicating a more complex structure within the reservoir.« less

Authors:
;
Publication Date:
Research Org.:
Los Alamos National Lab., NM
OSTI Identifier:
6719382
Report Number(s):
CONF-811036-
Journal ID: CODEN: SRSMC
Resource Type:
Conference
Journal Name:
Ser. Rock Soil Mech.; (United States)
Additional Journal Information:
Conference: 3. conference on acoustic emission/microseismic activity in geologic structures and materials, University Park, PA, USA, 5 Oct 1981
Country of Publication:
United States
Language:
English
Subject:
15 GEOTHERMAL ENERGY; GRANITES; ACOUSTIC EMISSION TESTING; HYDRAULIC FRACTURING; HOT-DRY-ROCK SYSTEMS; EARTHQUAKES; HYDRAULICS; ROCKS; SIMULATION; ACOUSTIC TESTING; COMMINUTION; ENERGY SYSTEMS; FLUID MECHANICS; FRACTURING; GEOTHERMAL SYSTEMS; IGNEOUS ROCKS; MATERIALS TESTING; MECHANICS; NONDESTRUCTIVE TESTING; PLUTONIC ROCKS; SEISMIC EVENTS; TESTING; 150201* - Geology & Hydrology of Geothermal Systems- USA- (-1989)

Citation Formats

Pearson, C, and Albright, J N. Acoustic emissions during hydraulic fracturing in granite. United States: N. p., 1984. Web.
Pearson, C, & Albright, J N. Acoustic emissions during hydraulic fracturing in granite. United States.
Pearson, C, and Albright, J N. Sun . "Acoustic emissions during hydraulic fracturing in granite". United States.
@article{osti_6719382,
title = {Acoustic emissions during hydraulic fracturing in granite},
author = {Pearson, C and Albright, J N},
abstractNote = {Hydraulic stimulation experiments being conducted in low-permeability crystalline rocks, at the Department of Energy's Hot Dry Rock Geothermal Site, Fenton Hill, New Mexico, often produce large numbers of microearthquakes. Typically, the early stages of these experiments are aseismic. The rate of acoustic emissions increases rapidly after a critical volume of water, equal to roughly two-thirds of the total amount previously injected, is exceeded, possibly indicating the onset of fracture extension. With local magnitudes ranging between -1 and -6, these events occurring at 3-km depth are too small to detect using surface seismometers, so we monitor the activity using a downhole triaxial geophone system(s) positioned in well(s) close to the reservoir volume. The system provided enough data in early experiments to locate the events using single station seismometry. Recently it became possible to station a second geophone system in a nearby well, that provides valuable additional constraints on event locations. The second tool was also used to measure relative changes in attenuation by comparing signal frequencies for the same event recorded on the two tools. P-wave attenuation does not vary significantly with the source region of the event, however, S-wave attenuation is quite variable, with Q ranging from 170 to 40. This suggests that the attenuation may be due to open water-filled fractures. We located large numbers of acoustic events during three hydraulic stimulation experiments, two of which occurred in March 1979 and one in December 1980. During the first two, event locations clustered near a single north-by-northwest trending vertical plane. During the third experiment (after an extended period of heat extraction) the same general trend was evident, but the zone was much wider and events seemed to occur on a series of parallel planes indicating a more complex structure within the reservoir.},
doi = {},
journal = {Ser. Rock Soil Mech.; (United States)},
number = ,
volume = ,
place = {United States},
year = {1984},
month = {1}
}

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