Integrated Anisotropic Rock Physics Model for Seismic Inversion
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Solution Overview
Problem
Current rock physics models fail to accurately simulate both shale and stress-induced anisotropy in sedimentary rocks, leading to inaccurate seismic inversion and interpretation, particularly in areas with high-impedance sands, and lack the ability to handle multiple anisotropy types simultaneously, while existing empirical models are data-driven and provide limited physical insight.
Innovation Solution
An integrated anisotropic rock physics model that divides the pore volume into clay-related, sand-related, and microcrack components, using mathematical relationships to quantify these parts based on overburden stress and shale volume, and applies anisotropic Gassmann theory for fluid mixture distribution, allowing for simultaneous simulation of shale and stress-induced anisotropy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If isotropic rock physics models are used, then the model simplicity is maintained, but the accuracy of seismic inversion and interpretation deteriorates due to inability to account for anisotropy
Solution Approach 1:
The patent segments the pore space into distinct components (clay-related pores, sand-related pores, and microcracks) and applies different anisotropic models to each component. This allows the complex anisotropic behavior to be modeled through composition of simpler sub-models, improving accuracy while managing complexity through modular structure.
Solution Approach 2:
The patent creates a composite rock physics model that integrates multiple anisotropic mechanisms (shale anisotropy from clay particles and stress-induced anisotropy from microcracks) into a unified framework. This composite approach allows simultaneous representation of different anisotropy types, resolving the contradiction between model simplicity and accuracy.
2Adaptability or versatility
If single-type anisotropy models are used, then the ease of operation is maintained, but the ability to simulate real sedimentary rocks deteriorates due to inability to handle multiple anisotropy types
Solution Approach 1:
The patent divides the pore space into distinct components (clay-related pores, sand-related pores, and microcracks) and applies different anisotropic models to each component. This segmentation allows the model to handle multiple anisotropy types simultaneously while maintaining operational simplicity through modular structure.
Solution Approach 2:
The patent creates a universal rock physics model framework that can simultaneously represent multiple anisotropy types (shale anisotropy from clay particles and stress-induced anisotropy from microcracks) through a unified mathematical structure, enabling the model to adapt to various geological conditions while maintaining ease of operation.
3Measurement precision
If empirical data-driven models are used, then the ease of manufacture is maintained, but the physical insight and accuracy deteriorate
Solution Approach 1:
The patent transforms empirical model parameters into physically meaningful parameters that represent actual rock properties (pore space characteristics, clay particle orientation, microcrack density). This allows the model to maintain accuracy while providing physical insight, as the parameters directly relate to measurable rock properties rather than being purely empirical fitting parameters.
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
The model provides accurate and efficient simulation of P- and S-wave velocities, improving seismic inversion and well log analysis by accounting for anisotropy, fluid distribution, and multiple anisotropy types, enhancing the accuracy of seismic data interpretation.
Implementation Method 1
placing the fluid mixture into the sand pores and microcracks of said model using anisotropic Gassmann theory
Implementation Method 2
In the major principal stress direction, the rock is compressed more in comparison with the compression at the other two directions. This differential compaction will result in a differential closure of soft pore, or cracks, in the rock.
Implementation Method 3
Shale anisotropy is caused by the preferred orientation of the pore space between the clay particles
Data Source
AI summary
Method for constructing an integrated rock physics model that simulates both shale anisotropy and stress-induced anisotropy of clastic rocks. In the model, the total pore volume is divided into three parts according to the estimated shale volume and effective stress: (1) clay-related pores, (2) sand-related pores, and (3) microcracks (mainly in the sand component). The pore space is then partitioned into the clay-related and sand-related pores using a scheme first disclosed by Xu and White in 1995. The model simulates shale anisotropy via the preferred orientation of clay-related pores and stress-induced anisotropy via the preferred orientation of microcracks, which is controlled by the differential stresses. Laboratory measurements or well logs are needed to establish a relationship between crack density and the effective stress.