[S-SS09] Seismic wave propagation: Theory and Application

[SSS09-P03] On the factors influencing ambient-noise passive seismic imaging

*Xin Guo¹, Zhihui Zou^1,2, Yongjun Rui³, Qinghui Cui³, Xinmin Shang³ (1.College of Marine Geosciences, Key Lab of Submarine Geosciences and Prospecting Techniques. MOE, Ocean University of China, Qingdao 266100, China, 2.Evaluation and Detection Technology Laboratory of Marine Mineral Resources, Qingdao National Laboratory for Marine Science and Technology, Qingdao 266061, China, 3.Geophysical Research Institute of Shengli Oilfield, Sinopec, Dongying, China 257022)

The passive seismic imaging method extracts the subsurface reflected signals using the cross-correlation of ambient noise. It has the advantages of low cost and little environmental damage, and can image the subsurface continuously. The passive seismic method has been applied in the fields of time-lapse monitoring the changes in petroleum reservoirs and mining processes. One of the effective passive seismic method is developed on the base of the seismic interferometry. The basic idea of seismic interference was proposed by Claerbout (1968) firstly, in which case the Green's function was estimated through the auto-correlation of seismic records generated by underground sources. In the exploration geophysics, Schuster et al. (2001) reconstructed the seismic wave field from the cross-correlation information using a generalized correlation of seismic data. Draganov et al. (2009) proposed a method based on cross-correlation to passively reconstruct the reflections using the seismic waveforms radiated from the underground sources. The workflow of passive seismic imaging is as follows: firstly, the seismic record is divided into a small time window for filtering analysis; secondly, select the panel dominated by body wave noise, and normalize each trace each panel; thirdly, select one trace as the position of virtual source shot to cross-correlate with other all traces; finally, stack them together to create one channel of the seismic record. A new seismic record is created by stacking the negative and positive parts. The main factors influencing the process of reflection extraction include: ①source distribution; ②wavelet type; ③seismic recording time; ④wavelet coherence. These factors are essential for the successful extraction of reflected signals, but systematic studies in this area are still lacking.

To analyze the influencing factors of the quality of passive reflected signals, we conduct a series of numerical tests. The effects of various factors on the quality of the reflection waves are compared and analyzed by synthesizing the virtual source seismic records from the transmitted wave response of underground passive sources. The results show that the denser the distribution of the seismic sources, the longer the recording time, and the stronger the incoherence of the seismic source, the better the quality of the synthetic reflection wave recording. By analyzing the factors that influence the construction of reflection waves, the processing flow of passive seismic exploration can be optimized to improve the quality of passive seismic imaging.