FREQUENCY-DOMAIN AUGMENTED TIME-DOMAIN FULL WAVEFIELD INVERSION

摘要

A basically time-domain method for performing full wavefield inversion of seismic data to infer a subsurface physical property model (61), where however at least one quantity required for the inversion, such as the Hessian of the cost function, is computed in the frequency domain (64). The frequency-domain quantity or quantities may be obtained at only a few discrete frequencies (62), preferably low frequencies, and may be computed on a coarse spatial grid, thus saving computing time with minimal loss in accuracy. For example, the simulations of predicted data and the broadband gradient of the objective function may be computed in the time domain (67), and the Hessian matrix, approximated by its diagonal, may be computed in the frequency domain. It may be preferable to use time-domain and the frequency-domain solvers that employ different numerical schemes, such as finite-difference method, one-way wave equation, finite-element method (63).

主权项

1. A method for inferring a model of velocity or other physical property by iteratively inverting measured seismic data, comprising the following steps, with (a) and (b) performed in either order:
(a) computing, using a computer, a cost function measuring misfit between the measured seismic data and simulated seismic data, and computing a gradient of the cost function with respect to parameters of the model; (b) computing a Hessian of the cost function; (c) computing an inverse of the Hessian and multiplying it times the gradient, thereby generating a conditioned gradient; (d) using the conditioned gradient to determine an update to the model; and (e) using the updated model to prospect for or produce hydrocarbons; wherein at least one of (a) and (b) is performed in frequency domain, but all other steps are performed in time domain.