Spectral Induced Polarization for Low Resistivity Pay Zone Detection

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Solution Overview

Problem

Existing methods struggle to accurately detect low resistivity pay (LRP) zones due to challenges in obtaining precise formation resistivity readings, measuring shaliness, and calculating water content, especially in formations affected by geological and engineering factors.

Innovation Solution

The implementation of the Spectral Induced Polarization (SIP) method, which involves obtaining SIP measurements across a wide frequency range (1 mHz-10,000 Hz) to determine frequency-dependent complex impedance values, allowing for the identification of LRP zones based on impedance dispersion patterns.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If conventional logging methods are used, then the measurement process is simple, but the ability to differentiate LRP zones is lost

Engineering Contradiction:

ImproveLRP zone detection accuracyVSAvoidlogging tool complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent applies parameter changes by measuring formation properties at multiple frequencies (1 mHz to 10,000 Hz) rather than a single frequency. This frequency-domain approach transforms the measurement parameter from static to dynamic, enabling differentiation of LRP zones through frequency-dependent impedance dispersion patterns that conventional single-frequency methods cannot detect.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent transitions from single-frequency to multi-frequency measurements, adding a frequency dimension to the traditional resistivity measurement. This dimensional expansion creates a spectral fingerprint for different formation types, allowing LRP zones to be distinguished from water zones based on their unique impedance dispersion characteristics across the frequency spectrum.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

2Measurement precision

If NMR tools are used, then irreducible water saturation can be estimated, but the depth of investigation is limited to flushed zones

Engineering Contradiction:

Improvewater saturation measurement accuracyVSAvoiddepth of investigation

Core Design Contradiction:

Measurement precisionVSLength of stationary object

Solution Approach 1:

The SIP method serves multiple functions: it measures both irreducible water saturation (like NMR) and provides deep formation evaluation beyond flushed zones. By measuring impedance dispersion at multiple frequencies, the method simultaneously characterizes both the flushed and unflushed zones, eliminating the depth limitation of NMR while maintaining water saturation measurement capability.

Inventive Principle:

Principle #6Universality (Multi-functionality)

3Measurement precision

If dielectric tools are used, then resistivity-independent saturation profiles can be obtained, but measurements are affected by invasion depth

Engineering Contradiction:

Improvewater saturation measurement accuracyVSAvoidinvasion depth interference

Core Design Contradiction:

Measurement precisionVSObject-affected harmful factors

Solution Approach 1:

The patent changes the measurement parameter from single-frequency resistivity to multi-frequency complex impedance. This transformation allows the system to separate the effects of invasion from true formation properties by analyzing how impedance varies with frequency. The frequency-dependent dispersion patterns provide invasion-depth-independent characterization of LRP zones, eliminating the harmful effect of invasion on saturation measurements.

Inventive Principle:

Principle #35Parameter changes

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 SIP method effectively differentiates LRP zones by analyzing frequency-dependent impedance values, providing a more comprehensive understanding of subsurface conditions and improving the accuracy of LRP zone detection.

Implementation Method 1

obtaining spectral induced polarization (SIP) measurements of a volume of a formation at a plurality of frequencies to determine a frequency-dependent complex (FDC) impedance value of a matrix material in the volume of the formation

Methodology Applied

Scientific EffectSpectral Induced Polarization:

Implementation Method 2

identifying the volume of the subsurface formation as the LRP zone when the FDC impedance value exhibits a dispersion at increasing frequencies

Methodology Applied

Scientific EffectImpedance dispersion:

Data Source

PatentUS20250180769A1Detection of low resistivity pay zones using spectral induced polarization method

Publication Date: 2025.06.05 KING FAHD UNIVERSITY OF PETROLEUM AND MINERALS

AI summary

A method of subsurface formation characterization is described. The method includes obtaining spectral induced polarization (SIP) measurements of a volume of a subsurface formation at a plurality of frequencies to determine a frequency-dependent complex (FDC) impedance value of a matrix material in the volume of the subsurface formation. The method further includes determining whether the volume is a low resistivity pay (LRP) zone with a formation resistivity index≤2, by analyzing the FDC impedance value of the matrix material, and identifying the volume of the subsurface formation as the LRP zone when the FDC impedance exhibits a dispersion at increasing frequencies. The FDC impedance value is substantially constant before the dispersion and increases by at least one order of magnitude over one order of magnitude of the increasing frequencies in the dispersion.