3D Mechanical Earth Model Calibration via Synthetic Stress Profiles

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Solution Overview

Problem

Current methods for predicting subsurface earth stresses, particularly horizontal principal stresses, are inadequate for practical engineering applications due to limitations in direct measurement frequency and accuracy, leading to significant predictive inaccuracies in hydraulic fracturing and other energy-related applications.

Innovation Solution

A method is developed to generate and calibrate three-dimensional earth models by creating synthetic principal horizontal stress profiles based on simplifications for isotropic formations, combined with data-driven relationships for anisotropic formations, and propagated through a 3D geocellular model using seismic facies, reducing reliance on detailed mineralogy and tectonic strain estimates.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If direct measurements (DFIT, image log analysis) are used to calibrate subsurface stresses, then measurement precision is improved, but the frequency and fine-scale characterization capability deteriorate

Engineering Contradiction:

Improvestress measurement precisionVSAvoidmeasurement frequency and fine-scale characterization capability

Core Design Contradiction:

Measurement precisionVSProductivity

Solution Approach 1:

The patent creates synthetic stress profiles that copy and extrapolate the characteristics of direct measurements across the entire subsurface volume. Instead of relying on sparse direct measurements, the system generates virtual stress field representations that maintain the precision of measured data while extending it throughout the model domain, enabling high-frequency and fine-scale characterization without additional field operations.

Inventive Principle:

Principle #26Copying

Solution Approach 2:

The patent replaces direct mechanical measurement systems (DFIT, image logs) with a computational modeling system that uses seismic data and mechanical earth models to substitute for physical stress measurements. This substitution allows continuous, high-resolution stress field characterization throughout the subsurface without the limitations of sparse direct measurements.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Area of stationary object

If conventional stress calculation methods using mineralogy logs and tectonic strain are used, then stress prediction coverage is improved, but manufacturing precision (predictive accuracy) deteriorates due to uncertainties in mineralogy and tectonic strain estimates

Engineering Contradiction:

Improvestress prediction coverageVSAvoidpredictive accuracy

Core Design Contradiction:

Area of stationary objectVSManufacturing precision

Solution Approach 1:

The patent changes the input parameters from uncertain mineralogy-based calculations to seismic-velocity-based mechanical earth models. By using seismic data to constrain elastic properties and stress fields directly, the system maintains broad spatial coverage while significantly improving predictive accuracy, as seismic data provides more reliable constraints on subsurface mechanical properties than mineralogy logs.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent introduces seismic data as an intermediary that bridges the gap between surface observations and subsurface stress fields. Seismic velocity data serves as a mediator that constrains the mechanical earth model, providing a more reliable basis for stress prediction than direct mineralogy or tectonic strain estimates, thereby improving accuracy while maintaining coverage.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Measurement precision

If detailed mineralogy logs and tectonic strain data are collected for stress calibration, then measurement precision is improved, but device complexity and data requirements increase

Engineering Contradiction:

Improvestress calibration precisionVSAvoiddata collection and processing complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent extracts and removes the complex mineralogy log analysis and tectonic strain calculation components from the stress calibration process. By using seismic data directly to constrain mechanical earth models, the system eliminates the need for detailed mineralogy logs and complex tectonic strain estimations, thereby reducing data collection and processing complexity while maintaining or improving calibration precision.

Inventive Principle:

Principle #2Taking out (Extraction)

Data Source

PatentUS20240272327A1Method and system to calibrate subsurface earth stresses in a geocellular model

Publication Date: 2024.08.15 EXXONMOBIL TECHNOLOGY & ENGINEERING CO

AI summary

A methodology for estimating stresses in the subsurface for the generation of a three dimensional (3D) mechanical earth model is provided. The method is executed via a processor of a computing system. The method includes generating a synthetic principal horizontal stress profile representative of a one-dimensional mechanical earth model (1D MEM) based on simplification that all formations are elastically isotropic. The method also includes combining the isotropically generated synthetic principal horizontal stress profile with an additional data-driven functional relationship for anisotropic formations to generate a global predictive conditional relationship based on a lithology dependent cutoff. The method also further includes generating a three-dimensional volume-based mechanical earth model using the global predictive conditional relationship.