Reflection imaging of deep reservoir structure based on three-dimensional hodogram analysis of multicomponent microseismic waveforms

摘要

We have applied a type of reflection technique, in which natural or induced microseismicity is used as a wave source and is processed in the time-frequency domain, to data from the Soultz Hot Dry Rock site to image deep structures within the reservoir that may be associated with flow paths among three wells. We selected and analyzed 119 good waveforms observed in 2003. The distribution of these 119 events was not strongly inclined, and although the selected number of events was much smaller than the total microseismic events located, we still succeeded in applying the reflection analysis. The reflection images obtained using waveforms from 2003 are in agreement with those obtained using data from 1993 and 2000. Finally, detailed three-dimensional reflection images were created by an integration of estimates using all available waveform data. Reflectors appear around the deep geothermal wells, and one of the dipping reflectors seems to be an obstacle to flow connection that shows a clear correlation with a microseismic cloud created during hydraulic stimulation in 2004. From these analyses we succeeded in interpreting the roles of preexisting structures in the development of flow connection among wells, which is an essential factor in a hot dry rock system.