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Surface Microseismic Imaging - Influence of High Velocity Layers
- Publisher: European Association of Geoscientists & Engineers
- Source: Conference Proceedings, 77th EAGE Conference and Exhibition - Workshops, Jun 2015, Volume 2015, p.1 - 5
Abstract
Summary
Imaging artifacts due to the influence of high velocity layers on the reduction of effective array aperture and the presence of increased multiples in the microseismic data are examined. FD full-waveform microseismic synthetics were generated that mimic a typical surface monitoring array for a range of 1D velocity models. Microseismic event locations using two different imaging techniques were compared: standard diffraction imaging (SDI) and moment tensor microseismic imaging (MTMI) algorithms. The results confirm that the presence of high velocity anhydrite layers reduce the overall aperture of a surface array, which results in poor resolution of imaged events, and a reduction in accuracy of event locations and effective monitoring area. The presence of high velocity lithological units also increases the amount of multiple and converted waves in the seismic data, resulting in an increase in coherent noise following the primary arrivals. Comparison of the two imaging procedures conclude that MTMI produces a much cleaner, less noisy image domain with more accurate and precise location estimations for similar monitoring scenarios, but both MTMI and SDI are equally affected by the presence of high velocity layers and recorded event frequency. For settings where high velocity lithological units are expected, the results of this study suggest that larger aperture arrays be deployed and the application of novel/advanced processing techniques be incorporated into the pre-processing of microseismic data to reduce multiple and converted wave noise.
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