Wei, Zhiyuan (CGG) | Xuan, Yi (CGG) | Huang, Rongxin (CGG) | Theriot, Christian (Shell Global) | Rodenberger, Douglas (Shell Global) | Chang, Mark (Anadarko Petroleum Corporation) | Morton, Scott (Hess) | Zouari, Mehdi (Anadarko)
Summary Large spectral differences exist between streamer and ocean bottom seismometer (OBS) data, mostly due to different surface-related ghost effects - streamer data have both shot-and receiver-side ghosts, while OBS data have only the shot-side ghost. In a recent OBSstreamer time lapse study in deepwater Gulf of Mexico, we investigated three schemes of spectral matching between OBS and streamer data: conventional 1D matching of streamer to OBS, receiver deghosting of streamer data only, and full deghosting of both data sets. The study demonstrated the benefits of receiver deghosting on streamer data over 1D matching, particularly because it provided a better match between the streamer and OBS data before migration and an increased 4D signal-to-noise ratio (S/N) after migration. However, we found that shot deghosting on both surveys did not improve the 4D results; instead, the spectra of streamer and OBS, especially at lower frequencies, were more different after shot deghosting. Receiver deghosting alone on the streamer data gave the best 4D results among the three schemes.
Elebiju, Bunmi (BP America) | Ariston, Pierre-Olivier (BP America) | van Gestel, Jean-Paul (BP America) | Murphy, Rachel (BP America) | Chakraborty, Samarjit (BP America) | Jansen, Kjetil (BP America) | Rodenberger, Douglas (Shell America) | White, Roy C. (Shell America) | Chen, Yongping (CGG) | Hren, David (CGG) | Hu, Lingli (CGG) | Huang, Yan (CGG)
Using the Kepler and Ariel Fields as a case study, this paper discusses the processing challenges and solutions applied to a 4D co-processing of Wide Azimuth Towed Streamer (WATS) on Narrow Azimuth Towed Streamer (NATS) data. Unlike a dedicated 4D acquisition, WATS on NATS 4D has relatively low repeatability in terms of acquisition geometry and bandwidth differences. All these factors can negatively impact the extraction of a meaningful 4D signal. In this paper, we demonstrate how processing techniques can help to increase repeatability and enhance 4D signal. We focus on the following 4D processing procedures: 4D co-binning, data matching, and post-migration co-denoise. Due largely to these techniques, the final co-processed volumes show an optimized 4D seismic signal with a median Normalized Root Mean Square (NRMS, which measures the repeatability between base and monitor. Details refer to Kragh and Christie, 2002) of 0.10 along the water bottom and 0.28 above the reservoir.