Induction Logging Non-Sinusoidal Current Waveforms
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Solution Overview
Problem
Existing induction logging tools face limitations in sensitivity and penetration depth due to sinusoidal current patterns, which result in weaker signal detection at greater depths and lower signal-to-noise ratios, making it difficult to accurately characterize earth formations.
Innovation Solution
The use of a non-sinusoidal electrical current with a first section having a uniform positive slope and a second section with a uniform negative slope, emitted by a transmitter antenna, to induce electromagnetic energy in the earth formation, allowing for improved signal reception and estimation of formation properties using a receiver antenna and processor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If sinusoidal current patterns are used in induction logging tools, then the tool operation is simple and continuous, but the signal detection sensitivity and penetration depth are limited
Solution Approach 1:
The patent changes the waveform parameter from sinusoidal to non-sinusoidal (specifically sawtooth or triangular waveforms). This parameter change allows for improved signal penetration depth and detection sensitivity by creating more distinct electromagnetic induction patterns in the formation, while the waveform generation remains implementable through standard pulse-width modulation techniques.
Solution Approach 2:
The invention employs periodic non-sinusoidal current patterns with specific duty cycles and rise/fall times. The periodic nature maintains continuous operation while the non-sinusoidal shape creates sharper transitions that enhance the electromagnetic induction effect, improving signal-to-noise ratio and detection capability.
2Measurement precision
If sinusoidal current patterns are used, then the electrical current control is simple, but the signal-to-noise ratio at greater depths is reduced
Solution Approach 1:
The patent modifies the current waveform parameters (rise time, fall time, duty cycle) to create non-sinusoidal patterns that generate stronger electromagnetic induction signals. These parameter changes improve the signal-to-noise ratio at depth while the control mechanism remains based on standard pulse-width modulation, keeping the implementation feasible.
Solution Approach 2:
The invention dynamically adjusts the current waveform parameters including rise time, fall time, and duty cycle based on operational requirements and formation characteristics. This dynamic control allows optimization of signal penetration and noise ratio while adapting to different logging conditions.
3Measurement precision
If conventional induction logging tools are used, then the device structure is simple, but the penetration depth and detection accuracy are limited
Solution Approach 1:
The patent employs antenna systems that can perform both transmission and reception functions, as well as tools that can measure multiple formation properties (resistivity, conductivity, fracture detection) using the same basic induction mechanism. This multi-functionality improves detection accuracy without proportionally increasing device complexity.
Solution Approach 2:
The invention changes the electromagnetic induction parameters by using non-sinusoidal current waveforms with specific frequencies and duty cycles. This allows conventional antenna structures to achieve enhanced detection accuracy and penetration depth through optimized electrical parameters rather than requiring fundamentally new hardware.
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 enhances the sensitivity and depth of signal penetration, resulting in more accurate characterization of earth formations with higher signal-to-noise ratios and improved detection of fractures and resistivity, particularly in deep and complex geological structures.
Implementation Method 1
a transmitter antenna disposed at the carrier and configured to emit electromagnetic energy into the earth formation
Implementation Method 2
a receiver antenna configured to receive a signal from the formation indicative of the property
Data Source
AI summary
An apparatus for estimating a property of an earth formation penetrated by a borehole includes: a carrier configured to be conveyed through the borehole; a transmitter antenna disposed at the carrier and configured to emit electromagnetic energy into the earth formation; a controller configured to control electrical current of frequency f transmitted to the transmitter antenna, wherein the transmitted electrical current is non-sinusoidal having a first section with a uniform positive slope and a second section with a uniform negative slope; a receiver antenna configured to receive a signal from the formation indicative of the property; and a processor configured to receive the signal from the receiver antenna and to estimate the property using the received signal.