Julian Drew

Microseismic event azimuth estimation: establishing a relationship between hodogram linearity and uncertainty in event azimuth

Summary : For microseismic data monitored and detected by a downhole vertical array, the polarization, or hodogram information, is needed to determine the event azimuth. To optimally weight when averaging over multiple measurements, we require knowledge of the uncertainties associated with each estimate. We discuss data acquired during a hydraulic stimulation. Using both synthetic data and observed events, by experiment we establish a relationship between the uncertainty in the estimated azimuth (or error), the signalto-noise ratio, and hodogram rectilinearity.

Complexities in the quick analysis and interpretation of microseismic data

Given that all points in the display are computed in the same way, the point location estimates likely all suffer in the same way from any bias. This can lead to a plot where the statistical distribution of points is misrepresentative of knowledge of the locations, and open to misinterpretation. This is particularly true when refined locations are computed, random errors may be reduced, but systematic errors likely remain.