2D MULTICOMPONENT TIME DOMAIN ELASTIC FULL WAVEFORM INVERSION

Abstract:

The search of hydrocarbon reservoirs between the finest stratigraphic and structural traps relies on the detailed surveying and interpretation of multicomponent seismic waves. This need makes Full Waveform Inversion (FWI) one of the most active topics in seismic exploration research and there are a limited number of FWI algorithms that undertake the elastic approach required to model these multicomponent data. We developed an iterative Gauss-Newton 2D time-domain elastic FWI scheme that reproduces the vertical and horizontal particle velocity as measured by common seismic surveys and obtains simultaneously the distribution of three elastic parameters of our subsurface model (density ρ and the Lame parameters λ and μ). The elastic wave is propagated in a heterogeneous elastic media using a time domain 2D velocity-stress staggered grid finite difference method. Our code observes the necessary stability conditions and includes absorbing boundary conditions and basic multi-thread parallelization. The same forward modeling code is also used to calculate the Frechet's derivatives with respect to the three parameters of our model following the sensitivity equation approach and perturbation theory. We regularized our FWI algorithm applying two different criteria: (1) First order Tikhonov regularization (maximum smoothness) and (2) Minimum Gradient Support (MGS) that adopts an approximate zero-norm of the several property gradients. We applied our algorithm to various test models and demonstrated that their structural information resemble closely those of the original three synthetic model parameters (λ, µ and ρ). Finally, we compared the role of both regularization criteria in terms of data fit, model stability and structural resemblance.