Surface Wave Tomography Applied to Oil and Gas Data

For land acquisition, the existence of shallow low velocity heterogeneous layer makes the imaging of the deep seismic reflection inconsistent, hence, the need of the velocity distributions for near surface layers. Surface wave tomography is a powerful tool to estimate the shallow subsurface. We present Rayleigh wave tomography on a dataset acquired for hydrocarbon exploration purposes along a seismic line. The processing to extract the dispersion curves (DCs) is performed using a two-station method that consists of computing the average phase slowness for each receiver pair illuminated by a source. The DCs extracted are then inverted, for different strategies, to obtain a shear wave velocity (VS) model representative of the shallow subsurface. The good fitting of experimental and synthetic DCs generated during inversion, as well as the high coverage provided by the cross-paths make the results reliable. Finally, the inversion is validated by the checkerboard test. A MATLAB routine is implemented to provide the coverage by plotting each path in its corresponding wavelength range colored by its average velocity.