Enhanced Monitoring of Geologic Carbon Sequestration Using 3-D Passive Microseismic Location Techniques
In recent years there has been a significant increase of interest in real-time passive monitoring of microseismicity related to carbon dioxide sequestration in geological formations. We have adapted a sophisticated 3-D location algorithm originally designed for regional and teleseismic applications to microseismic monitoring of shallow underground reservoirs. Our technique has many features that are of significant value to small-scale applications, such as the accommodation of down-hole stations, the use of azimuth data in addition to arrival times, travel-time forward modeling with 3-D velocity models, and the computation of 3-D confidence regions on the calculated hypocenters. In addition to modifying the location algorithm, we also developed a wavelet-based phase detection algorithm to accurately pick microseismic P and S arrival times and a polarization algorithm to determine the arrival azimuths of P waves. To date we have applied the microseismic version of our location algorithm to two data sets, including a field study of hydraulic fracturing following fluid injection at a site in southeast Texas and a synthetic study using the geometry from a small-scale carbon injection pilot site. The results from both case studies demonstrate that we can accurately locate and characterize microseismicity in a realistic 3-D velocity model using both arrival times and azimuths measured by a sparse network of downhole sensors.
AAPG Search and Discovery Article #90090©2009 AAPG Annual Convention and Exhibition, Denver, Colorado, June 7-10, 2009