The effect of location error on microseismic mechanism estimation: synthetic and real field data examples

The decomposing of the full moment tensor of micro¬seismic events observed during hydraulic fracture stimulations into double couple (%DC), compen¬sated linear vector dipole (%CLVD), and isotropic (%ISO) components has been shown to be useful for making more complete characterizations of these events (Williams-Stroud, 2008). While this information about the nature and geometry of a fracture is important and very telling, any source of potential error in these decomposi¬tions must be taken into account. One source of particular importance to microseismic monitoring is the effect of loca¬tion error on the full moment decomposition. With this type of analysis becoming more prevalent, there is concern as to whether the effect of location error on potential interpreta¬tions and recommendations based on microseismic fracture geometry is thoroughly understood. Moment tensor inversion of microseismic data is an immensely powerful interpretation tool. An understanding of the nature of the rock failure supports the development of discrete fracture networks (DFN), reservoir simulation models, and stimulated reservoir volume estimates. Such interpretations are a large part of the driving force behind the growth in microseismic monitoring. Furthermore, a proper characterization of the event mechanism is necessary in full waveform imaging of microseismic data to properly account for the radiation pattern of the signals (Duncan, 2010).