US 9,702,993 B2 · Multi-parameter inversion through offset dependent elastic FWI

Abstract

Method for multi-parameter inversion using elastic inversion. This method decomposes data into offset/angle groups and performs inversion on them in sequential order. This method can significantly speed up convergence of the iterative inversion process, and is therefore most advantageous when used for full waveform inversion (FWI). The present inventive approach draws upon relationships between reflection energy and reflection angle, or equivalently, offset dependence in elastic FWI. The invention uses recognition that the amplitudes of small angle (near offset) reflections are largely determined by acoustic impedance alone (1), independent for the most part of Vp/Vs. Large angle (middle and far offset) reflections are affected by Ip, Vp/Vs (2) and other earth parameters such as density (3) and anisotropy. Therefore, the present inventive method decomposes data into angle or offset groups in performing multi-parameter FWI to reduce crosstalk between the different model parameters being determined in the inversion.

Claims11

Dependent claims

A computer-implemented method for full wavefield inversion of seismic data to infer subsurface physical property parameters including P-wave (pressure wave) velocity, S-wave (shear wave) velocity, and density, comprising:

extracting only PP mode (P-wave down/P-wave up) from the seismic data, and inverting, with a full wavefield inversion algorithm, the PP mode data sequentially in two or more different offset ranges, each offset range full wavefield inversion determining at least one physical property parameter, wherein in a second and subsequent full wavefield inversions, parameters determined in a previous inversion are held fixed, and further wherein all full wavefield inversions are performed using a computer;
and
generating, with a computer, a subsurface physical property model that includes the P-wave velocity, S-wave velocity, and the density from the full wavefield inversion algorithm, which transforms the seismic data into the subsurface physical property model, wherein the subsurface physical property model is a quantitative rock-property description of a hydrocarbon reservoir, and using the subsurface physical property model for geophysical prospecting.

Dependencies are inferred from the claim text.

Multi-parameter inversion through offset dependent elastic FWI

Life of this patent

Multi-parameter inversion through offset dependent elastic FWI

Life of this patent

Abstract

Claims11