oa Tomographic Velocities - Challenges and Applications

The resolution of seismic imaging has long been characterized by a mid-frequency gap between the long vertical wavelength components that can be inferred from travel-time tomography and the short vertical wavelength components that can be inferred from seismic migration. The progress in tomography and in broadband acquisition now allows this mid-wavelength gap to be filled and even results in the overlapping between the resolution obtained from velocity model building and from seismic migration. Recent progress in tomographic approaches now provides vertical resolution up to 6 Hz, with in addition, a precise localization of the velocity contrasts. With a case study we discuss their benefits for reservoir characterization, where the missing frequencies are traditionally coming from a model interpolated/extrapolated from well log information. If the seismic inversion for reservoir characterization is not sensitive to the low-to-mid frequencies, this low-to-mid frequency modelling is critical for the estimation of absolute rock properties, and replacing a model extrapolated from sparse well information by actual measurements is of paramount importance.