Micromechanical Elastic Properties Solver for Heterogeneous Reservoirs
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Solution Overview
Problem
Current methods for estimating elastic properties of subterranean rock formations, particularly in non-conventional layers like shale and mudstone, are inaccurate and unreliable due to their heterogeneity and ductile behavior, and existing micromechanical approaches are inefficient in modeling stress fields along wellbores with limited mineralogy data.
Innovation Solution
A computer-implemented method using continuum micromechanics to model the composite mechanical behavior of multiphase heterogeneous rock formations, deriving continuous mechanical properties based on mineralogy data and eigenstrains, which does not rely on acoustic wave speeds and can be applied to horizontal wells, employing Eshelby's inclusion method and multi-mineral micromechanical solutions to link elastic rock properties with rock composition and texture.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If sonic-based methods are used to estimate elastic properties, then the approach works well in conventional reservoirs, but it becomes inaccurate and unreliable in non-conventional rock layers such as shale, mudstone or marl
Solution Approach 1:
The invention changes the fundamental parameters used for estimation from dynamic sonic-based measurements to static mineralogy-based micromechanical properties. By using mineral composition data and micromechanical models instead of acoustic wave speeds, the method adapts to non-conventional reservoirs where sonic methods fail due to heterogeneity and ductile behavior.
Solution Approach 2:
The invention replaces the acoustic wave-based mechanical measurement system with a mineralogy-based micromechanical modeling system. Instead of measuring dynamic elastic properties through sonic logs and converting them empirically, the method directly calculates static elastic moduli from mineral composition using micromechanical theories, eliminating the unreliable dynamic-static transform step.
2Ease of manufacture
If empirical dynamic-static transforms are used to convert dynamic moduli to static moduli, then the process is simple, but the results are inaccurate for heterogeneous and ductile rock formations
Solution Approach 1:
The invention replaces the empirical transformation process with a first-principles micromechanical calculation approach. Instead of using empirical correlations to convert dynamic to static moduli, the method directly computes static elastic moduli from mineral composition data using micromechanical models, eliminating the source of inaccuracy while maintaining computational efficiency.
Solution Approach 2:
The invention changes the input parameters from dynamic sonic measurements to static mineralogy data. By using mineral composition and applying micromechanical models that directly predict static elastic properties, the method bypasses the need for dynamic-static transformation entirely, thereby improving accuracy without significantly increasing complexity.
3Measurement precision
If laboratory testing of numerous rock samples is performed to analyze mechanical variations, then detailed mechanical properties can be obtained, but physical sampling is scarce in reservoir settings
Solution Approach 1:
The invention creates a virtual model of the rock formation's mechanical properties by copying and utilizing mineralogy data from logging tools. Instead of requiring physical rock samples for laboratory testing, the method uses in-situ mineral composition measurements and applies micromechanical models to predict mechanical properties continuously along the wellbore, providing detailed analysis without needing scarce physical samples.
4Productivity
If cross-plotting dynamic elastic properties versus porosity is performed to derive empirical relationships, then field-wide empirical models can be created, but the approach does not provide continuous mechanical properties in horizontal wells
Solution Approach 1:
The invention replaces the cross-plotting and empirical relationship derivation approach with a deterministic micromechanical calculation system. By using mineralogy data and micromechanical models, the method provides continuous mechanical property predictions along the entire wellbore trajectory, including horizontal sections, without relying on empirical correlations that require vertical depth-based sampling and plotting.
Data Source
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AI summary
This disclosure describes a novel method for predicting continuous wellbore mechanical properties such as static elastic stiffness and failure strength, where the properties solutions are deterministic and based on mechanical theory. It has at least three immediate applications: (a) continuous plots of mechanical properties vs. depth, (b) conceptual testing of the effect of changing constituent volume fractions, (c) ternary plots.