Wu Xiao, Liu Yang, Wang Yong, Xu Shi-Gang, and Jia Wan-Li
1. State Key Laboratory of Petroleum Resources and Prospecting, China University of Petroleum (Beijing), Beijing 102249,China.
2. Faculty of Petroleum, Karamay Campus of China University of Petroleum (Beijing), Karamay, Xinjiang 834000, China.
3. CNPC Key Laboratory of Geophysical Prospecting, China University of Petroleum (Beijing), Beijing 102249, China.
4. Sinopec Geophysical Exploration Institute of Jiangsu Oilfield, Jiangsu, 210046, China.
Abstract：
The conventional fast converted-wave imaging method directly uses backward Pand converted S-wavefield to produce joint images. However, this image is accompanied by strong background noises, because the wavefields in all propagation directions contribute to it. Given this issue, we improve the conventional imaging method in the two aspects. First, the amplitude-preserved P- and S-wavefield are obtained by using an improved space-domain wavefield separation scheme to decouple the original elastic wavefield. Second, a convertedwave imaging condition is constructed based on the directional-wavefield separation and only the wavefields propagating in the same directions used for cross-correlation imaging, resulting in effectively eliminating the imaging artifacts of the wavefields with different directions; Complex-wavefield extrapolation is adopted to decompose the decoupled P- and S-wavefield into directional-wavefields during backward propagation, this improves the efficiency of the directional-wavefield separation. Experiments on synthetic data show that the improved method generates more accurate converted-wave images than the conventional one. Moreover, the improved method has application potential in micro-seismic and passive-source exploration due to its source-independent characteristic.
2019, Vol. 16 
