Seismic Reflection Forward Model for Sediment Property Quantification
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current seismic-reflection profiling methods using single-channel acoustic systems are limited in their ability to quantify sediment physical properties of the seabed and subbottom layers due to the lack of unique determination of sound velocity and the empirical, non-mathematically rigorous nature of existing models like the Biot-Stoll model, which relies on empirical values and lacks precision in predicting acoustic properties of individual marine sediments.
Innovation Solution
A method is developed to quantify seabed sediment composition and subbottom structure using a forward model that describes the physical relationships between material and acoustic properties, incorporating a viscoelastic formulation to describe squirt-flow processes and considering the sediment as a bimodal grain-size distribution with complex and frequency-dependent bulk and shear moduli, allowing for the estimation of sound velocity, density, porosity, permeability, and composition from traveltime, attenuation, and reflectivity data.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the Biot-Stoll model is used to determine acoustic properties of unconsolidated marine sediments, then the model can provide a framework for calculating velocity and attenuation, but the model relies on empirical values and postulated grain-to-grain friction, leading to non-mathematically rigorous predictions and lack of precision for individual sediments
Solution Approach 1:
The patent changes the fundamental parameters of the Biot-Stoll model by replacing the postulated grain-to-grain friction mechanism with a viscoelastic frame model. This substitution transforms the empirical framework into a mathematically rigorous one, allowing precise calculation of acoustic properties from fundamental material parameters without relying on empirical adjustments.
Solution Approach 2:
The patent replaces the mechanical friction-based Biot-Stoll model with a viscoelastic mechanics approach. By substituting the friction postulate with viscoelastic deformation theory, the model achieves mathematical rigour while maintaining physical relevance for unconsolidated sediments, enabling precise prediction of acoustic properties.
2Adaptability or versatility
If single-channel seismic-reflection profiling data is used to characterize seabed sediments, then the method can provide qualitative overview of large-scale geological features, but the method cannot uniquely determine sound velocity without further knowledge
Solution Approach 1:
The patent introduces a viscoelastic frame model as an intermediary that bridges the gap between seismic reflection data and acoustic property determination. This model acts as a mediator that transforms the limited single-channel seismic data into precise sound velocity and attenuation values by incorporating fundamental material parameters through viscoelastic theory.
Solution Approach 2:
The patent changes the approach to sound velocity determination by transitioning from direct acoustic measurement to indirect determination through viscoelastic frame parameters. This parameter transformation enables unique determination of sound velocity from single-channel seismic data without requiring additional knowledge, thereby improving measurement precision while maintaining application versatility.
3Adaptability or versatility
If the Biot-Stoll model is used with postulated grain-to-grain friction, then the model can describe acoustic wave propagation in unconsolidated sediments, but the model adds non-linear components that depend on particle displacement magnitude
Solution Approach 1:
The patent replaces the non-linear friction-based Biot-Stoll model with a linear viscoelastic frame model. This substitution eliminates the non-linear particle displacement dependence while maintaining applicability to unconsolidated sediments, thereby stabilizing the acoustic response composition and enabling more reliable predictions.
Solution Approach 2:
The patent changes the constitutive relationship from non-linear friction to linear viscoelastic deformation. This parameter change transforms the model from one with non-linear particle displacement dependence to one with linear, stable acoustic response, while preserving the model's adaptability to unconsolidated sediment conditions.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach provides a more mathematically rigorous prediction of acoustic properties of unconsolidated marine sediments, enabling accurate determination of layer thicknesses and material properties, improving upon previous models by incorporating local fluid flow and stress-induced processes, and allowing for the generation of synthetic seismograms and inversion of seismic data.
Implementation Method 1
The occurrence in unconsolidated sediment of processes of this kind had been postulated earlier by Stoll (1985) without proposing a mathematical description on the basis of a geometrical model
Implementation Method 2
These are generally known as local fluid flow ('squirt flow'). The occurrence in unconsolidated sediment of processes of this kind
Implementation Method 3
Pore fluid viscosity, η
Data Source
AI summary
The present invention discloses a method for the quantitative characterisation of a seabed sediment composition and a seabed's layered subbottom structure from at least one normal-incidence, single-channel reflection acoustic amplitude time series seismogram. The method detects a plurality of reflections from subbottom interfaces in said seismograms, determines the traveltime, the polarity and the reflectivity of each detected reflection, determines the intrinsic attenuation of the sediment layer between pairs of adjacent reflections, and determines the acoustic properties, layer thicknesses and material properties of the seabed's layered subbottom structure as a function of said traveltimes, polarities and reflectivities of the detected reflections and said intrinsic attenuation of the sediment layer between pairs of adjacent reflections. The invention also discloses a forward model describing the physical relationship between the material properties and the acoustic properties of seabed sediments.