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 a deeper tow position, which creates additional drag, and noise recorded by the vertical particle velocity sensor. These restrictions have limited 3-D acquisition to a maximum towing depth of 20 m whilst 25 m towing depth is routinely used for 2-D acquisition. In July 2013, a field trial was performed with a slanted streamer, from 15m depth at the front to 30m at larger offsets. Since the front of the streamer is deployed at a depth routinely used for dual sensor streamer acquisition, such a slanted streamer profile is no more operationally difficult to achieve and has comparable noise performance to a horizontal streamer. Wavefield separation can be performed for arbitrary streamer profiles and the up-going wavefield output at a horizontal datum, thereby presenting no additional difficulties for subsequent processing steps. The benefit of deploying a substantial proportion of the streamer at greater depth is increased low frequency signal-to-noise ratio (less than 16 Hz). This uplift was demonstrated by comparing the data acquired using a slanted streamer profile to that obtained using a horizontal streamer.