Sub-Basalt Imaging West of Shetland
West of Shetland
In order to achieve sufficient bandwidth in areas where high frequencies are limited, it is necessary to extend the low frequencies. Lower frequencies are affected less by attenuation, and provide greater accuracy and stability for seismic inversion.
Conventional marine streamer acquisition lacks sufficient signal-to-noise ratio in the 2-7 Hz bandwidth due to streamer depth, streamer tow noise, source array configuration, source depth and source bubble. Using BroadSeis we routinely record frequencies down to 2.5 Hz, providing three octaves of data below 20 Hz.
In trials West of Shetland, BroadSeis shows superior sub-basalt imaging and penetration. In the example above, the marked reflector fades away beneath the thicker basalt towards the northwest (left) on the conventional section. Only the lower frequencies provided by BroadSeis penetrate the basalt, allowing the reflector to be traced across the entire section. There is also improved fault definition (center) on the BroadSeis data as well as significant improvement to the S/N ratio at depth.
Zooming in around the top and base basalt (above) shows the clearer definition of this layer on the BroadSeis data. We can see the base and intra basalt layers, including probable multiple basalt flows pinching out.