Low Frequency Complex Resistivity Logging Tool
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Solution Overview
Problem
Current induced polarization (IP) logging technologies are limited in determining fluid saturation in geological formations due to their focus on high frequency dielectric principles, which can only assess resistivity a few millimeters into the formation, failing to effectively evaluate hydrocarbon reserves and resources at deeper levels.
Innovation Solution
A tool with transmitter-receiver spacings in the order of meters operating between 0.01 Hz and 1000 Hz is used to measure low-frequency complex resistivity, allowing for the assessment of larger and deeper volumes of interest by inducing and detecting electromagnetic fields, and processing these signals to determine formation parameters such as porosity, permeability, and fluid saturation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If high frequency dielectric principles are used for IP logging, then measurement precision at shallow depths is improved, but the ability to assess deeper formation volumes deteriorates
Solution Approach 1:
The patent changes the frequency parameter from high frequency (MHz range) to low frequency (0.01-1000 Hz range) to enable deeper penetration into the formation. This parameter change allows the electromagnetic fields to penetrate beyond the shallow millimeter-level depth limitation of high frequency methods, while still maintaining measurement capability through specialized transmitter-receiver configurations operating in the low frequency regime
2Volume of stationary object
If transmitter-receiver spacing is increased to meters, then the volume of formation assessed is improved, but the signal detection difficulty worsens
Solution Approach 1:
The patent changes the operating frequency parameter to low frequencies (0.01-1000 Hz) which enables meter-scale transmitter-receiver spacing while maintaining detectable signal levels. The low frequency operation reduces signal attenuation over distance, allowing the electromagnetic fields to propagate through larger formation volumes without becoming undetectably weak
Solution Approach 2:
The patent replaces conventional high frequency electromagnetic measurement systems with a low frequency system that uses specialized transmitters and receivers. This substitution enables the system to operate with meter-scale spacing by exploiting the different propagation characteristics of low frequency electromagnetic fields, which attenuate less over distance compared to high frequency signals
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
This approach enables the determination of complex resistivity at deeper levels, providing more accurate assessments of hydrocarbon reserves and resources by measuring fluid saturation and other formation parameters over larger volumes, enhancing hydrocarbon evaluation and production monitoring.
Implementation Method 1
applying a transmit input signal to a transmitter coil of the transmitter to cause the transmitter to output a transmit output signal into the formation, wherein the transmit output signal is an electromagnetic field
Implementation Method 2
receiving from a receiver a formation signal, wherein formation signal is based on canceling the transmit output signal from a signal received by the receiver, the formation signal being a voltage indicative of an induced polarization in the formation
Data Source
AI summary
A logging tool having a transmitter and receiver is positioned in a geological formation. While the logging tool is static, a transmit input signal is applied to a transmitter to cause the transmitter to induce a transmit output signal in the form of an electromagnetic field into a formation. While the logging tool is static, a formation signal is received based on the transmit output signal. The formation signal may be a voltage indicative of an induced polarization in the formation based on the transmit output signal. A complex resistivity of the formation is determined based on the formation signal.