Increased streamer depth for dual-sensor acquisition - Challenges and solutions

The towing depth applicable to dual-sensor streamer acquisition has hitherto been limited by operational challenges associated with maintaining the fronts of the streamers at deeper tow positions, which creates additional drag, and noise recorded by the particle velocity sensor. These restrictions have limited 3-D acquisition to a maximum tow depth of 20m whilst 25m towing depth is routinely used for 2-D acquisition. In July 2013, a field trial was performed with streamers towed at 15m at the front increasing to 30m depth at mid- and large- offsets. Since the front of the streamer is deployed at a depth routinely used for dual-sensor acquisition, such a streamer profile is no more difficult to achieve and has comparable noise performance to a horizontal streamer. Wavefield separation can be performed for arbitrary streamer profiles and the upgoing wavefield output at a horizontal datum, thereby presenting no additional difficulties for subsequent processing steps. The benefit of deploying the streamer at a greater average depth is increased low frequency signal-to-noise ratio (frequencies below 16 Hz). This uplift was demonstrated by comparing the deep tow data to that obtained using a horizontal streamer at 15m depth.