Dielectric Permittivity Spectrum Determination in Rock Formations
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Solution Overview
Problem
Current methods for determining the dielectric permittivity spectrum of underground rock formations, particularly in oil or gas wells, are limited in their ability to accurately interpret electromagnetic measurements below 106 Hz, which is crucial for understanding rock properties and fluid saturation.
Innovation Solution
A method involving a series of electromagnetic measurements at specific frequencies, including one above 108 Hz and two below 107 Hz, to determine the frequency-dependent dielectric permittivity spectrum, using a relationship to decode the data and estimate pore size distribution and fluid salinity, leveraging wireline and LWD resistivity and dielectric logging tools across a wide frequency range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of information
If dielectric measurements are made at frequencies below 10^6 Hz, then useful information about formation properties can be obtained, but the interpretation becomes inconsistent and difficult
Solution Approach 1:
The patent applies parameter changes by utilizing measurements across a broad frequency spectrum (from very low frequencies below 10^6 Hz to high frequencies above 10^8 Hz) and transforming the raw dielectric data into a standardized spectral representation. This allows consistent interpretation of formation properties despite variations in measurement frequency, effectively resolving the inconsistency problem while preserving information from low-frequency measurements.
2Measurement precision
If electromagnetic measurements are made at multiple frequencies to determine dielectric permittivity spectrum, then accurate characterization of rock properties and fluid content is achieved, but the measurement and interpretation complexity increases
Solution Approach 1:
The patent segments the frequency spectrum into distinct measurement ranges (very low frequencies below 10^6 Hz, high frequencies above 10^8 Hz, and intermediate frequencies) and applies appropriate interpretation methods to each segment. This segmentation allows accurate determination of the dielectric permittivity spectrum while managing complexity by treating different frequency ranges with tailored approaches rather than attempting a unified complex interpretation.
Solution Approach 2:
The patent introduces an intermediary spectral representation that serves as a bridge between raw multi-frequency electromagnetic measurements and rock property characterization. By transforming measurements into a standardized spectral format, the intermediary representation simplifies the interpretation process while maintaining the accuracy benefits of multi-frequency measurements.
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
Enables accurate determination of the dielectric permittivity spectrum, allowing for better characterization of rock properties and fluid content, improving the interpretation of rock microstructure and fluid properties by isolating distinct polarization processes across various frequency ranges.
Implementation Method 1
fluid-saturated rocks have dispersive electromagnetic properties, i.e. frequency-dependent dielectric permittivity and conductivity
Implementation Method 2
EPT (Electromagnetic Propagation Tool) of Schlumberger, operating at 1.1 GHz where the dispersion is minimum
Data Source
AI summary
A method for determining the frequency-dependent dielectric permittivity spectrum of a rock sample, comprising:—defining a series of electromagnetic measurement data comprising at least a first measurement at a frequency from which a substantially frequency-independent value of dielectric permittivity ∈∞, can be obtained; and at least second and third measurements at different frequencies from which values for frequency-dependent dielectric permittivity ∈rock (f) can be obtained; and—using the first, second and third measurements to determine the frequency-dependent spectrum of the sample.