Dispersion estimation by nonlinear optimization of beam-formed fields

摘要

A method for estimating velocity dispersion in seismic surface waves in massive 3-D data sets (401) that improves upon auto-picking of a curve along the peak or ridge of the magnitude of the beam-formed field (402). The seismic data are transformed to the frequency-slowness domain, where nonlinear constrained optimization is performed on the transformed data. The optimization matches a nonlinear mathematical parametric model (403) of a beam-formed field to that in the transformed data, adjusting the parameters each iteration to reduce mismatch (404). Dispersion curves are determined by the center of the beam in the optimized models (405). A preferred nonlinear parametric mathematical model is a Gaussian-shaped beam or a cosine-tapered boxcar beam.

主权项

1. A computer-implemented method for processing seismic data from a subsurface region to obtain indication of hydrocarbon potential of the subsurface region, comprising:
estimating velocity dispersion of seismic surface waves in the subsurface region by a method comprising transforming the seismic data to frequency-slowness domain resulting in a beam-formed field, and then modeling the beam-formed field with an analytic dispersion beam and fitting the beam-formed field with the analytic dispersion beam by performing nonlinear constrained optimization; using the estimated seismic velocity dispersion in processing the seismic data or in determining local earth properties in the subsurface region; and using the processed seismic data or the local earth properties for determining presence, quality or other characteristic of hydrocarbon reservoirs; wherein at least the nonlinear constrained optimization is performed using a computer, and wherein the estimated seismic velocity dispersion is determined at locations throughout the subsurface region and is compiled, by a computer, into a 3-D dispersion volume, which is used for further processing of the seismic data to remove unwanted surface-wave noise or to characterize near-earth-surface properties.