Orthorhombic full-waveform inversion for imaging the Luda field using wide-azimuth ocean-bottom-cable data

Ocean Bottom Cable (OBC) acquisition has become the new trend in Bohai area with the benefit of operational flexibility, better illumination, better multiple elimination and better S/N for the targets at middle to deep depth. However, the presence of orthorhombic anisotropy causes severe challenges in imaging with Wide Azimuth (WAZ) OBC data, particularly fault imaging which is sensitive to velocity accuracy. Fault imaging can be smeared and fault shadows can be observed within complex strike-slip fault systems if the azimuthal dependency of wave propagation is not properly honored and velocity variation across faults is not properly modelled. To address these challenges encountered in imaging of Luda field with WAZ OBC data, we have developed a practical orthorhombic full-waveform inversion approach to invert for a high-resolution model in the presence of orthorhombic anisotropy. We will demonstrate that our orthorhombic FWI approach can produce high resolution velocity model which reconciles the structural discrepancies between seismic images from different azimuths, and significantly improves the focusing of the fault imaging and the imaging of structures beneath the faulting system. The combined effect of these improvements gives a clear uplift in the final seismic image.