Velocity model optimization for surface microseismic monitoring via amplitude stacking

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• 作者：Haiyu Jiang ; Zhongren Wang ; Xiaoxian Zeng ; Hao Lü ; Xiaohua Zhou ; Zubin Chen ; ^{czb@jlu.edu.cn}
• 关键词：Velocity model optimization ; Surface microseismic monitoring ; Very fast simulated annealing ; Amplitude stacking ; Error compensation
• 刊名：Journal of Applied Geophysics
• 出版年：2016
• 出版时间：December 2016
• 年：2016
• 卷：135
• 期：Complete
• 页码：317-327
• 全文大小：2797 K
• 卷排序：135

文摘

A usable velocity model in microseismic projects plays a crucial role in achieving statistically reliable microseismic event locations. Existing methods for velocity model optimization rely mainly on picking arrival times at individual receivers. However, for microseismic monitoring with surface stations, seismograms of perforation shots have such low signal-to-noise ratios (S/N) that they do not yield sufficiently reliable picks. In this study, we develop a framework for constructing a 1-D flat-layered a priori velocity model using a non-linear optimization technique based on amplitude stacking. The energy focusing of the perforation shot is improved thanks to very fast simulated annealing (VFSA), and the accuracies of shot relocations are used to evaluate whether the resultant velocity model can be used for microseismic event location. Our method also includes a conventional migration-based location technique that utilizes successive grid subdivisions to improve computational efficiency and source location accuracy. Because unreasonable a priori velocity model information and interference due to additive noise are the major contributors to inaccuracies in perforation shot locations, we use velocity model optimization as a compensation scheme. Using synthetic tests, we show that accurate locations of perforation shots can be recovered to within 2 m, even with pre-stack S/N ratios as low as 0.1 at individual receivers. By applying the technique to a coal-bed gas reservoir in Western China, we demonstrate that perforation shot location can be recovered to within the tolerance of the well tip location.