Antenna System Parameter Estimation in EM Logging
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Solution Overview
Problem
Existing electromagnetic logging techniques in boreholes face challenges in accurately determining formation properties due to changes in antenna system parameters, such as impedance and resonance frequency, which can lead to misinterpretation of formation characteristics during drilling operations.
Innovation Solution
The method involves using calibration signals with different frequencies to estimate antenna system parameters like transfer function, resonance frequency, and quality factor, allowing for real-time adjustments of measurement signals and excitation signals to compensate for changes and improve data accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional electromagnetic logging techniques are used without calibration, then the logging process is simpler and faster, but the measurement precision deteriorates due to antenna system parameter changes
Solution Approach 1:
The patent applies preliminary action by performing calibration measurements before actual formation logging. Calibration signals are sent through the antenna system to determine baseline antenna parameters (inductance, capacitance, resistance) before the antenna interacts with the formation. This preliminary characterization allows the system to compensate for subsequent parameter changes during logging operations, improving measurement precision without requiring continuous complex calibration during the actual measurement process.
Solution Approach 2:
The patent implements feedback by continuously monitoring antenna system parameters during logging operations and using this information to correct measurement readings. The system measures actual antenna parameters (such as resonance frequency and quality factor) during the logging process and feeds this information back to adjust the formation property calculations. This feedback mechanism compensates for antenna parameter drift and maintains measurement accuracy throughout the logging operation.
2Reliability
If antenna system parameters are not monitored, then the device complexity is lower, but the reliability of formation property measurements deteriorates due to parameter drift
Solution Approach 1:
The patent uses feedback to monitor antenna system parameters in real-time during logging operations and adjust measurements accordingly. The system continuously measures actual antenna characteristics and compares them against expected values, using this feedback to detect parameter drift and correct formation property measurements. This ensures reliable logging data even when antenna parameters change due to environmental factors or wear.
Solution Approach 2:
The patent addresses parameter changes by explicitly measuring and accounting for variations in antenna system parameters (inductance, capacitance, resistance, resonance frequency) during logging operations. Rather than assuming fixed antenna characteristics, the system dynamically tracks parameter changes and incorporates this information into the formation property calculations, maintaining measurement reliability despite antenna degradation or environmental effects.
3Measurement precision
If calibration signals are sent at multiple frequencies, then the measurement precision improves through better antenna characterization, but the use of energy increases due to additional signal transmission
Solution Approach 1:
The patent applies preliminary action by performing comprehensive calibration at the beginning of the logging operation to establish baseline antenna parameters. By characterizing the antenna system in advance using multiple frequencies, the system can reduce the need for continuous high-frequency calibration signals during actual logging. The preliminary calibration data is used to create reference profiles that guide subsequent measurements, reducing overall energy consumption while maintaining precision.
Solution Approach 2:
The patent uses partial action by sending calibration signals at a limited number of discrete frequencies rather than continuously sweeping through the entire frequency range. The system selects specific frequencies that are sufficient to characterize the antenna's key parameters (resonance frequency, quality factor, impedance) without requiring excessive energy. This partial calibration approach provides adequate antenna characterization while minimizing energy consumption compared to full continuous frequency sweeping.
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 more precise estimation of formation properties by accounting for antenna system changes, reducing errors and enhancing the reliability of logging operations during drilling.
Implementation Method 1
Properties of the formation may be estimated by creating electromagnetic (EM) excitation in the formation with at least one transmitter, and receiving related signals at one or more receiver antennas
Implementation Method 2
feeding a calibration signal into a signal path of the antenna system to generate a resultant signal; estimating at least one value of the at least one antenna system parameter by using the resultant signal
Data Source
AI summary
Systems, methods, and devices for evaluation of an earth formation intersected by a borehole using a logging tool. Methods include performing EM logging in a borehole intersecting an earth formation using a measurement signal from an antenna system in the borehole, the measurement signal dependent upon a parameter of interest of the formation and at least one antenna system parameter of the antenna system, comprising feeding a calibration signal into a signal path of the antenna system to generate a resultant signal; estimating at least one value of the at least one antenna system parameter by using the resultant signal; and performing further logging operations in dependence upon the at least one value of the at least one antenna system parameter. The calibration signal comprises at least two calibration subsignals with a first calibration subsignal having a first frequency and a second calibration subsignal having a second frequency.