Fast location of seismicity: A migration-type approach with application to hydraulic-fracturing data

Abstract

We propose a new approach for the location of seismic sources using a technique inspired by Gaussian-beam migration of three-component data. This approach requires only the preliminary picking of time intervals around a detected event and is much less sensitive to the picking precision than standard location procedures. Furthermore, this approach is characterized by a high degree of automation. The polarization information of three-component data is estimated and used to perform initial-value ray tracing. By weighting the energy of the signal using Gaussian beams around these rays, the stacking is restricted to physically relevant regions only. Event locations correspond to regions of maximum energy in the resulting image. We have successfully applied the method to synthetic data examples with 20%–30% white noise and to real data of a hydraulic-fracturing experiment, where events with comparatively small magnitudes [Formula: see text] were recorded.

Influence of a velocity model and source frequency on microseismic waveforms: some implications for microseismic locations

“…As discussed earlier, the range of source frequencies can vary depending on several factors. In a previous study of Cotton Valley microseismicity, Rentsch et al (2007) observe a dominant frequency of 100 Hz. It is not uncommon, however, to observe dominant frequencies down to the 10's of Hz (e.g., Teanby et al, 2004) and up to the 100's Hz (e.g., Trifu et al, 2000).…”

“…For the hodogram approach, travel time phase picks and a velocity model are required. The semblance technique (e.g., Duncan and Eisner, 2010) is similar to migration and involves propagating the microseismic energy back to its hypocenter using a Green's function (e.g., Kirchhoff, Gaussian beam and oneway wave equation migration) and does not require arrival time phase picks (e.g., Rentsch et al, 2007;Duncan and Eisner, 2010). It is important to stress that in all three approaches a velocity model is required.…”

Microseismic Imaging of Hydraulically Induced-Fractures in Gas Reservoirs: A Case Study in Barnett Shale Gas Reservoir, Texas, USA

“…In Semblance technique (e.g. [19]) a single phase arrival, applied in large aperture array, or multiple phases arrivals , suitable for small aperture of the downhole arrays, are utilized to determine a point in the space, correspond to the hypocenter location, that maximize the semblance measure. Semblance technique does not depend on discrete arrival times to image the source location and therefore is conceptually similar to Kirchhoff migration.…”

Simultaneous microseismic event localization and source mechanism determination

“…Haldorsen et al (2013) use projected traces in the frequency domain for stacking. Rentsch et al (2007) apply the stacking procedure to the energy of 3C data weighted with a Gaussian-beam-type factor. However, none of the above-mentioned techniques resolved the destructive interference due to polarity reversals from the microseismic sources.…”