Full text loading...
-
Inversion of Seismic Refraction and Reflection Data for Long-wavelength Velocity Model
- Publisher: European Association of Geoscientists & Engineers
- Source: Conference Proceedings, 76th EAGE Conference and Exhibition 2014, Jun 2014, Volume 2014, p.1 - 5
Abstract
We have applied wave-equation tomography to both refraction and reflection data to retrieve the long-wavelength subsurface velocity model. To simulate reflection waves, especially, long- and short-wavelength structures are separated and mapped into velocity and density, respectively. To match the amplitude of the real reflection waves, full waveform inversion is applied to the near-offset data, where all the short-wavelength impedance contrasts are mapped into density. The short-wavelength density model is then converted into zero-offset travel time domain where it is independent of the long-wavelength velocity model. As velocity is updated using wave-equation tomography, density is converted back into depth domain for wave-field modeling. To alleviate the nonlinearity of the inversion problem, an offset continuation strategy is adapted that refraction waves are used first to provide vertical constrains on the velocity model, after which, reflection waves are included to provide lateral constrains. As wave-equation tomography has derived the satisfactory long-wavelength velocity model, FWI is initialized to invert all the data to retrieve the short-wavelength velocity structures. The strategy is applied to one marine real dataset example with 15-km-long streamer. Our results shows that one can recover detailed velocity information starting from a poorly constrained model with appropriate regularization.