Cross-Flow Noise Attenuation and Imaging of Ultra-Low Frequencies in Multivessel Circular Shooting Acquisition Surveys

Effective noise attenuation is essential to deliver high-quality seismic images that preserve the integrity of the subsurface structures, particularly in deep-water subsalt environments where signal is relatively weak.

Among the noise sources affecting marine seismic data, one of the strongest is the flow of water moving along or across the streamer. Water moving along the streamer is partly caused by swell. Water moving across the streamers is dependent on the movement of the streamer in the water and on currents. The severity of noise generated by the movement of this water increases if we tow the streamers in a circular fashion.

We present a method to attenuate the dominant types of noise affecting towed-streamer marine seismic data in a dual-vessel circular acquisition in deep-water Gulf of Mexico. Then, we demonstrate the value that the significant information present in the data at ultra-low frequencies, below 4 Hz, brings to imaging. This noise attenuation method capitalizes on the fine sampling of the single-sensor acquisition system used (3.125-m trace spacing) to spatially interpolate the noise beyond aliasing and apply smear-free dip filters in the unaliased tau-p domain, where the noise (low velocity) is sparse and can be discriminated from the signal.