Seismic Quality Factor Estimation via Weighted Log-Amplitude Fitting

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Solution Overview

Problem

Current methods for estimating seismic quality factor Q are limited by sensitivity to absolute scaling and fail to utilize the entire bandwidth of seismic signals, leading to inaccurate interval value determinations, especially in deepwater reservoirs with complex stratigraphy.

Innovation Solution

A method that involves preprocessing seismic data to estimate amplitude spectra, taking logarithms, deriving weights, and performing a weighted fit using a function parameterized by an initial wavelet, an attenuation (1/Q) profile, and an absolute-scaling profile to determine interval values of seismic quality factor Q, which is insensitive to absolute scaling and utilizes the entire bandwidth.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If the spectral ratio method is used to estimate Q, then the estimation process is simple, but the measurement precision is limited with variance of errors never less than about 50%

Engineering Contradiction:

Improvesimplicity of estimation processVSAvoidprecision of Q estimation

Core Design Contradiction:

Ease of manufactureVSMeasurement precision

Solution Approach 1:

The patent changes the fundamental parameters used in Q estimation from simple spectral ratios to a comprehensive model incorporating initial wavelet characteristics, attenuation profiles, and absolute scaling factors. This transforms the estimation approach from a simple ratio comparison to a multi-parameter fitting process that accounts for the entire bandwidth of seismic signals, thereby improving measurement precision while maintaining computational feasibility through automated fitting procedures

Inventive Principle:

Principle #35Parameter changes

2Stability of the object's composition

If the Gabor-transform technique is used to estimate Q, then a global solution consistent with a single effective waveform is obtained, but the method only works for a single depth-independent Q value and is sensitive to absolute scaling

Engineering Contradiction:

Improveconsistency of waveform solutionVSAvoidability to handle depth-dependent Q variations

Core Design Contradiction:

Stability of the object's compositionVSAdaptability or versatility

Solution Approach 1:

The patent segments the seismic signal analysis into multiple depth-dependent components, allowing different Q values to be estimated at different depths. Instead of forcing a single global Q value, the method divides the propagation path into intervals and estimates attenuation characteristics for each interval, thereby capturing depth-dependent variations in quality factor while maintaining waveform consistency through the fitting framework

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent adds the depth dimension to the Q estimation problem, transforming it from a single-value parameter to a depth-dependent function. By incorporating depth as an additional dimension in the fitting model, the method can simultaneously estimate initial wavelet characteristics, attenuation profiles varying with depth, and absolute scaling factors, thereby achieving both waveform consistency and adaptability to depth-dependent conditions

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

3Measurement precision

If the frequency shift method is used to infer interval attenuation, then the approach is insensitive to absolute scaling, but it relies on simplifying assumptions about the spectra of input waveforms

Engineering Contradiction:

Improveinsensitivity to absolute scalingVSAvoidsimplifying assumptions about waveform spectra

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent changes the approach from relying on simplifying spectral assumptions to explicitly modeling the full waveform characteristics including initial wavelet shape, attenuation profile, and absolute scaling. By parameterizing the complete waveform model rather than assuming simple spectral forms, the method eliminates the need for simplifying assumptions while maintaining insensitivity to absolute scaling through the relative fitting approach

Inventive Principle:

Principle #35Parameter changes

4Productivity

If conventional methods are used to estimate Q, then the processing is computationally efficient, but the resolution is limited by low-pass filtering effects of the earth

Engineering Contradiction:

Improvecomputational efficiencyVSAvoidseismic resolution

Core Design Contradiction:

ProductivityVSMeasurement precision

Solution Approach 1:

The patent substitutes the conventional spectral ratio approach with a comprehensive waveform fitting model that utilizes the entire bandwidth of seismic signals. By replacing the simple ratio calculation with a multi-parameter fitting procedure that incorporates initial wavelet characteristics, attenuation profiles, and absolute scaling, the method extracts more information from the same data, thereby improving resolution without requiring additional computational resources for data acquisition

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Data Source

PatentUS7376517B2Method for estimation of interval seismic quality factor

Publication Date: 2008.05.20 CHEVRON USA INC

AI summary

The present invention includes a method for determining interval values of seismic quality factor, Q, from seismic data. Seismic data is recorded and preprocessed as necessary. Estimates of amplitude spectra are determined from the seismic data. Logarithms are taken of the amplitude spectra and weights derived from the amplitude spectra. Interval values of seismic quality factor, Q, are determined by performing a weighted fit to the log-amplitude spectra with a function that is parameterized by an initial wavelet, an attenuation profile (1/Q) and an absolute-scaling profile.