Full Waveform Inversion (FWI) has become a new tool in recent practice for subsurface velocity model updating. When using FWI, the common scheme was to use data sets which have relatively large offsets up to 8 km or more and frequencies as low as 2.8 Hz considering surface seismic acquisition. In terms of the marine environment, Wide Azimuth towed streamer (WAZ) or Ocean Bottom Cable (OBC) data collection provide the above mentioned specifications. Recent advances in acquiring data such as the dual coil method offer significant improvements in characteristics over WAZ and OBC such as better illumination, lower frequencies, and longer offsets which allow the FWI to more accurately determine the velocity field. In this paper, the data set that we input to FWI is a result of dual-coil acquisition where the maximum offset is up to 14300 m with full azimuth distribution. In order to approximate the observed data, the acoustic inversion incorporates anisotropy, in the finite difference propagators and uses the true source and receiver depth. Our results demonstrate that FWI can be used for velocity update with the long offsets and low frequencies provided by the above described dual coil seismic acquisition. In particular, the shallow section of the model can be significantly enhanced by using FWI which can result in an improved overall depth image. Furthermore, lower frequencies and longer offsets mitigate the sensitivity of inversion to the initial velocity model by enabling FWI to update the low wave-number component of the velocity model. Finally, we show the reverse time migration depth image improvements by using the FWI developed velocity field versus that one from the ray-based methodology.


Over the past few years, 3D FWI with the acoustic wave equation has been applied to real datasets in marine (Plessix, 2009, Sirgue at al., 2010, Vigh et al., 2010, 2011) and in land (Plessix, 2010) environments. These results have demonstrated that FWI can be used to update the velocity if the acquired data contain low enough frequencies and long enough offsets. In particular, the shallow section of the model can be significantly enhanced by using full-waveform inversion which can result in a more improved overall depth image. One of difficulties with FWI is the convergence to the local minima that makes the technique very sensitive to the starting velocity model especially when 3D is considered. To mitigate the sensitivity to the initial velocity field, low frequencies and long offsets are required (Bunks et al., 1995, Pratt, 1999) which enables FWI to update the low-frequency component of the velocity model.

This content is only available via PDF.
You can access this article if you purchase or spend a download.