Strong coal-seam reflection suppression by fast ma-tching pursuit based on dictionary learning
HAN Zhanyi1, SONG Wei2, LI Jiguang1, ZHAO Cuixia1, ZHAO Aiguo1, MA Xiaoyi1
1. Geophysical Research Institute, SINOPEC Shengli Oilfield, Dongying, Shandong 257022, China; 2. College of Geophysics, China University of Petroleum (Beijing), Beijing 102249, China
Abstract:Weak effective signals are usually hidden in the upper, lower, and internal parts of strong coal-seam reflection signals. The research on methods to effectively separate weak effective signals from strong coal-seam reflection signals has attracted more and more attention, and matching pursuit is one of the effective algorithms to solve this problem. In the early days, the Gabor wavelet was used as the generating function of the matching wavelet, some other theoretical wavelets such as Morlet and Ricker wavelets are commonly used now, which are greatly different from the waveform characteristics of actual seismic data, which results in the generation of residual components in the matching process. To solve these problems, this paper introduces the dictionary learning algorithm to learn the atoms of the dictionary in the seismic data instead of predefining the atoms, which greatly improves the matching degree of signal decomposition. Aiming at the problem of unstable coal-seam reflection in the target area, we carry out dictionary learning according to a single event to build a unimodal dictionary with different amplitude, phases, dominant frequency, and polarity. Through the analysis of the attenuation of strong coal-seam reflection of post-stack and pre-stack data, it is verified that the new method is more reliable and effective than the conventional method in strong reflection suppression. The high-resolution time-frequency analysis of Wigner-Ville distribution based on the matching wavelet reveals the time-frequency attribute characteristics before and after the elimination of strong coal-seam reflection, which can provide technical support for accurate description of reservoirs near coal seams.
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