Velocity Model Update via Decomposed Full Waveform Inversion Gradient

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Solution Overview

Problem

Existing full waveform inversion methods struggle to update low wavenumber components of velocity models at greater depths, especially when recorded data lacks coherent energy at low frequencies, leading to incomplete subsurface property characterization.

Innovation Solution

A decomposed full waveform inversion gradient is used to suppress high wavenumber components while preserving low wavenumber components, allowing for updates at greater depths by dynamically weighting the velocity sensitivity kernel, enabling the inclusion of low-frequency information and improving resolution.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If conventional full waveform inversion methods are used to update velocity models, then high wavenumber components can be updated, but low wavenumber components at greater depths cannot be updated due to lack of coherent energy at low frequencies

Engineering Contradiction:

Improvevelocity model resolutionVSAvoidlow wavenumber component information

Core Design Contradiction:

Measurement precisionVSLoss of information

Solution Approach 1:

The inversion gradient is decomposed into separate wavenumber components (low wavenumber and high wavenumber parts). This segmentation allows selective processing where low wavenumber components are updated using refracted energy and high wavenumber components are updated using reflected energy, resolving the information loss problem at different depth ranges

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different updating strategies are applied to different wavenumber components based on their specific characteristics. Low wavenumber components use one updating approach optimized for deep penetration, while high wavenumber components use another approach optimized for shallow resolution, achieving locally optimal updates for each component type

Inventive Principle:

Principle #3Local quality

2Manufacturing precision

If the velocity model is updated using reflected energy, then high wavenumber components are provided, but low wavenumber components at greater depths are suppressed

Engineering Contradiction:

Improvevelocity model update accuracyVSAvoidsuppression of low wavenumber components

Core Design Contradiction:

Manufacturing precisionVSObject-generated harmful factors

Solution Approach 1:

Instead of using only reflected energy for updates, the method inverts the approach by using refracted energy specifically for updating low wavenumber components. This reverse strategy compensates for the suppression effect and ensures complete wavenumber coverage

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

The updating process combines multiple energy types (reflected and refracted) and multiple wavenumber components into a composite update strategy. This composite approach leverages the strengths of each energy type to achieve comprehensive velocity model updates across all depth ranges and wavenumber spectra

Inventive Principle:

Principle #40Composite materials

Data Source

PatentEP3387467B1Velocity model update with an inversion gradient

Publication Date: 2019.09.25 PGS GEOPHYSICAL AS

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Figure 3A~4B

AI summary

The present disclosure is related to a velocity model update with a full waveform inversion gradient. At least one method can include updating a velocity model of a subsurface, which can include suppressing high wavenumber components of the velocity model provided by reflected energy with a decomposed full waveform inversion gradient. Low wavenumber components can be preserved in the velocity model.