Using Surface and Downhole Data to Drive Developments in Event Detection Algorithms

Summary We have identified individual waveforms from microseismic events and tracked them from reservoir to surface using a wide aperture borehole seismic array, as well as across surface seismic lines. We noted that deeper arrivals in the long borehole array contained complex triplications that could potentially pose difficulties for event detection and location techniques that rely on identifying the direct arrivals. By modelling full waveform synthetics we were able to reconstruct the principal features of these complex arrivals for the long borehole array. We have developed an extension to the CMM approach to extract the appropriate arrival times via STA/LTA processing of the full waveform synthetics. These times are then used to augment the first arrival P and S travel times in the objective function used for CMM processing, allowing the energy in complex arrivals to be identified and beam-formed in the event detection algorithm. Mode converted arrivals may also be used in the subsequent Geiger relocation step to provide greater aperture with which to refine the event location.