Show simple item record

dc.contributor.advisor Pratson, Lincoln en_US
dc.contributor.advisor Malin, Peter en_US
dc.contributor.author Kahn, Dan Scott en_US
dc.date.accessioned 2008-08-01T12:53:13Z
dc.date.available 2008-08-01T12:53:13Z
dc.date.issued 2008-04-10 en_US
dc.identifier.uri http://hdl.handle.net/10161/646
dc.description Dissertation en_US
dc.description.abstract <p>The mapping of induced seismicity in enhanced geothermal systems presents the best tool available for understanding the resulting hydro-fractured reservoir. In this thesis, two geothermal systems are studied; one in Krafla, Iceland and the other in Basel Switzerland. The purpose of the Krafla survey was to determine the relation between water injection into the fault system and the resulting earthquakes and fluid pressure in the subsurface crack system. The epicenters obtained from analyzing the seismic data gave a set of locations that are aligned along the border of a high resistivity zone ~2500 meters below the injection well. Further magneto-telluric/seismic-data correlation was seen in the polarity of the cracks through shear wave splitting. The purpose of the Basel project was to examine the creation of a reservoir by the initial stimulation, using an injection well bored to 5000 meters. This stimulation triggered a M3.4 event, extending the normal range of event sizes commonly incurred in hydro-fractured reservoirs. To monitor the seismic activity 6 seismometer sondes were deployed at depths from 317 to 2740 meters below the ground surface. During the seven-day period over 13,000 events were recorded and approximately 3,300 located. These events were first located by single-difference techniques. Subsequently, after calculating their cross-correlation coefficients, clusters of events were relocated using a double-difference algorithm. The event locations support the existence of a narrow reservoir spreading form the injection well. Analysis of the seismic data indicates that the reservoir grew at a uniform rate punctuated by fluctuations which occurred at times of larger events, which were perhaps caused by sudden changes in pressure. The orientation and size of the main fracture plane was found by determining focal mechanisms and locating events that were similar to the M3.4 event. To address the question of whether smaller quakes are simply larger quakes scaled down, the data set was analyzed to determine whether scaling relations held for the source parameters, including seismic moment, source dimension, stress drop, radiated energy and apparent stress. It was found that there was a breakdown in scaling for smaller quakes.</p> en_US
dc.format.extent 6146194 bytes
dc.format.mimetype application/pdf
dc.language.iso en_US
dc.subject Geophysics en_US
dc.title Hydro-Fractured Reservoirs: a Study Using Double-Difference Location Techniques en_US
dc.type Dissertation en_US
dc.department Earth and Ocean Sciences en_US
duke.embargo.months 12 en_US
dc.date.accessible 2009-08-02T05:00:03Z

Files in this item

This item appears in the following Collection(s)

Show simple item record