Frequency Ratiometric Resistivity Logging Tool Data Processing
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Solution Overview
Problem
Conventional resistivity logging tools face challenges with amplitude and phase noise, timing errors, and spatial errors due to the sequential measurement of frequency responses, which complicates the synchronization of transmitter and receiver antennas during drilling operations.
Innovation Solution
The method involves simultaneous transmission of multiple signals at known frequencies and amplitudes, allowing for frequency ratiometric processing to calculate relative measurements, thereby minimizing errors and eliminating the need for precise synchronization between transmitter and receiver antennas.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If sequential measurement of frequency responses is used, then timing and spatial errors occur due to movement and rotation of the bottom hole assembly, but simultaneous transmission of multiple signals complicates the system synchronization requirements
Solution Approach 1:
The patent combines multiple frequency transmissions into a single simultaneous operation. The transmitter antenna transmits multiple signals at different frequencies at the same time, and the receiver antenna receives all frequencies simultaneously. This merging of sequential operations into a simultaneous process eliminates timing errors caused by bottom hole assembly movement and rotation, while the frequency ratiometric processing simplifies the synchronization requirements.
Solution Approach 2:
The patent changes the measurement parameter from absolute frequency response values to a ratio of frequency responses at different frequencies. By calculating the ratio between responses at different frequencies rather than measuring absolute values, the system eliminates the need for precise timing synchronization between transmitter and receiver, as the ratio remains valid regardless of slight timing variations.
2Adaptability or versatility
If multiple antenna assemblies are used for absolute resistivity measurements, then more comprehensive formation characterization is achieved, but amplitude and phase noise increases that cannot be corrected via calibration
Solution Approach 1:
The patent converts the harmful effect of amplitude and phase noise into a beneficial outcome by using frequency ratiometric processing. Instead of trying to eliminate or correct the noise through calibration, the system calculates the ratio of responses at different frequencies, which causes the common-mode noise to cancel out. This transforms the noise problem into a solution that inherently rejects the interference while maintaining comprehensive formation characterization capability.
3Measurement precision
If low drift clocks and signal telemetry are deployed for synchronization, then timing accuracy is improved, but device complexity and cost increase
Solution Approach 1:
The patent makes the measurement system self-sufficient by eliminating the need for external synchronization infrastructure. The frequency ratiometric processing method allows the receiver to accurately measure formation resistivity using only the relative frequency responses, without requiring synchronized clocks or complex telemetry systems. The system serves itself by using the ratio calculation to inherently compensate for any timing variations, removing the need for additional synchronization components.
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 reduces timing and spatial errors, enhances the accuracy of resistivity logging data, and supports a wide range of resistivity logging-while-drilling tools without affecting the depth of investigation, enabling more reliable characterization of subterranean formations.
Implementation Method 1
a given transmitter antenna transmits two or more electromagnetic signals at two or more known frequencies through a borehole fluid to a given receiver antenna
Implementation Method 2
two or more frequency responses are subsequently received at the given receiver antenna for frequency ratiometric processing
Data Source
Figure 1~2
Figure 3A~3B
Figure 4~5
AI summary
A method includes introducing a resistivity logging tool including one or more transmitter coils and one or more receiver coils into a wellbore. First and second signals are then transmitted with a first transmitter coil at first and second frequencies, respectively, and a first receiver coil receives first and second response signals based on the first and second signals. A ratio between the first and second response signals is then calculated to obtain a ratio signal, and the ratio signal is processed in an inversion algorithm. One or more formation characteristics of the subterranean formation may then be determined based on the ratio signal as processed by the inversion algorithm.