Rock Permeability Stress Testing for In Situ Flow Estimates
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Solution Overview
Problem
The challenge of quantifying rock permeability under various anisotropic stress conditions is crucial for predicting fluid production rates, particularly hydrocarbon production rates, as increased effective stress reduces permeability, making fluid extraction difficult.
Innovation Solution
A method and system are employed to determine in situ permeability by subjecting a rock sample to sequences of confining stress, axial stress, and pore pressure triplets (CSASPP) in a laboratory setting, using a permeability system to establish stress sensitivity parameters and models, allowing for the determination of in situ permeability based on these parameters and models.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If increased effective stress is applied to the rock, then the rock strength and stability are improved, but the permeability is reduced making fluid extraction difficult
Solution Approach 1:
The patent applies parameter changes by systematically varying stress conditions (confining stress, axial stress, pore pressure) to measure permeability at different stress states. This allows characterization of how permeability changes with stress, enabling prediction of fluid flow under various production conditions while accounting for the strength-stress relationship.
2Ease of manufacture
If traditional permeability measurement methods are used, then the measurement process is simple, but the measurement precision under anisotropic stress conditions is insufficient
Solution Approach 1:
The patent segments the permeability measurement process into multiple distinct stress condition tests (constant confining stress with varying axial stress, constant axial stress with varying confining stress, constant pore pressure conditions). This segmentation allows precise characterization of permeability under different anisotropic stress states while maintaining systematic and manageable test procedures.
Solution Approach 2:
The patent employs dynamic stress application where confining stress, axial stress, and pore pressure are varied systematically during testing. This dynamic approach allows measurement of permeability across a range of stress conditions rather than at a single static state, significantly improving measurement precision for anisotropic stress characterization.
Data Source
AI summary
Methods and systems are disclosed. The methods may include determining a first sequence of permeabilities by subjecting a rock sample to a first sequence of confining stress, axial stress, pore pressure (CSASPP) triplets and determining a first rock parameter using the first sequence of permeabilities, the first sequence of CSASPP triplets, and a first permeability model. The methods may further include determining a second sequence of permeabilities by subjecting the rock sample to a second sequence of CSASPP triplets and determining a second rock parameter using the second sequence of permeabilities, the second sequence of CSASPP triplets, and the first permeability model. The method may still further include determining an in situ permeability for an in situ rock based on an initial permeability, a second stress sensitivity parameter, a first stress sensitivity parameter, a confining stress value, axial stress values, a pore pressure value, and a second permeability model.