Hunting S-waves using 4C seismic data in the carbonates, offshore UAE

The multi-component sea-bottom seismic technology has been developed in the last several decades. The technology is often simply referred to as 4C where four-component data are acquired in marine environments consisting of pressure and three displacement components (X-Y-Z). 4C seismic data have been used as better P (pressure) wave data but there has also been a significant use of converted data; typically this has been P-wave down to the reflector and S-wave up. For the Arabian Gulf offshore UAE we typically have shallow water and very strong reflectors near the seabed. So far converted wave modes have been of little use there. In previous studies (Sun et al, 2009 and Berteussen and Sun, 2010) we have performed seismic modeling and compared the modeling results with real data. This has helped us understand the complex wave-field that often looks extremely noisy. One conclusion from that work is that we expect to find PS-S waves, i.e. waves that have been converted from P to S near the sea-bottom and then have continued as S-waves. In this work, we report on a test to extract such converted waves (PS-S). We utilize velocity models based on nearby log data and the knowledge established in our previous work to design a model dependent work-flow that extracts the PS-S. We demonstrate that it does indeed work and that we do indeed obtain S-wave records with an acceptable signal-to-noise ratio. To our knowledge this is the first time that such wave modes have been demonstrated in this region.