Passive Seismic Interferometry and Anisotropic Eikonal Phase-velocity Tomography with Examples from Ekofisk Field
S. de Ridder, B. Biondi and D. Nichols
Event name: 76th EAGE Conference and Exhibition 2014
Session: Applications of Seismic (Time-lapse) Interferometry
Publication date: 16 June 2014
Info: Extended abstract, PDF ( 1.46Mb )
Price: € 20
We derived an anisotropic eikonal tomography method for phase velocities based on a two-dimensional elliptical-anisotropic wave equation. The method is applied to Scholte-waves emitted between 0.2 and 1.3 Hz by virtual seismic sourced from stations in the Life of Field Seismic (LoFS) Ocean Bottom Cable (OBC) array installed over Ekofisk field. The virtual seismic sources are created by passive seismic interferometry of 40 hours of noise recordings from Ekofisk’s LoFS array. Azimuthal-anisotropic Scholte-wave velocities form a large circular pattern over the Ekofisk field and are result from the overburden stress-state and from sea-floor subsidence induced by decades of hydrocarbon extraction. A dispersion analysis shows that the Scholte-wave virtual seismic source exhibits a peak sensitivity between 160 and 565 m below the sea floor. These results are significant because they show that noise recordings made at Ekofisk’s LoFS array can be used to monitor azimuthal-anisotropy in the near surface.