From Bureau of Economic Geology, The
University of Texas at Austin (www.beg.utexas.edu).
Bureau Seminar, February 15, 2008
Basel Deep Heat Mining: A Study of a Hydro-Fractured Reservoir
Ph.D. student, Duke University
The primary purpose of the Basel Deep-Heat Mining Project stimulation was to create a hydro-fractured reservoir. During a seven-day period over 13,000 events were recorded. Approximately 3,300 of those events could be accurately located, and nearly one hundred of them were of magnitude one or greater. The project was halted because a M3.4 event was triggered by the stimulation. Double-difference location techniques were used to determine the hypocenters, and the event locations indicated the creation of a narrow reservoir which spread from the injection well. By mapping similar events, the minimum fault plane associated with the M3.4 event was determined. This plane was consistent with the focal mechanism independently calculated for the event and with the source dimension determined from the seismograms. The reservoir grew at a uniform rate with significant fluctuations that were correlated with changes in the injection parameters and with the larger seismic events. The data set was also analyzed to determine whether scaling relations held for the source parameters. The relations between the seismic moment and radiated energy for small events were different from those for larger events, indicating a breakdown in scaling for smaller quakes.