Data processing of the Kuiyang-ST2000 deep-towed high-resolution multichannel seismic system and application to South China Sea data

The Kuiyang-ST2000 deep-towed high-resolution multichannel seismic system was designed by the First Institute of Oceanography, Ministry of Natural Resources (FIO, MNR). The system is mainly composed of a plasma spark source (source level: 216 dB, main frequency: 750 Hz, frequency bandwidth: 150-1 200 Hz) and a towed hydrophone streamer with 48 channels. Because the source and the towed hydrophone streamer are constantly moving according to the towing configuration, the accurate positioning of the towing hydrophone array and the moveout correction of deep-towed multichannel seismic data processing before imaging are challenging. Initially, according to the characteristics of the system and the towing streamer shape in deep water, travel-time positioning method was used to construct the hydrophone streamer shape, and the results were corrected by using the polynomial curve fitting method. Then, a new data-processing workflow for Kuiyang-ST2000 system data was introduced, mainly including float datum setting, residual static correction, phase-based moveout correction, which allows the imaging algorithms of conventional marine seismic data processing to extend to deep-towed seismic data. We successfully applied the Kuiyang-ST2000 system and methodology of data processing to a gas hydrate survey of the Qiongdongnan and Shenhu areas in the South China Sea, and the results show that the profile has very high vertical and lateral resolutions (0.5 m and 8 m, respectively), which can provide full and accurate details of gas hydrate-related and geohazard sedimentary and structural features in the South China Sea.