Concentric Electrode Sensor Standoff Correction
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Solution Overview
Problem
Conventional resistivity sensors in drilling apparatus face challenges in accurately measuring standoff distances due to vibration and irregular borehole shapes, leading to inconsistent and inaccurate corrections during resistivity imaging.
Innovation Solution
A sensor system with a plurality of return electrodes and a transmitter electrode arranged in a concentric manner, injecting alternating currents of different frequencies to measure effective impedance, which compensates for standoff distances and provides accurate imaging by selecting appropriate readings and using an artificial neural network for improved data processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional resistivity sensors are used with mechanical or acoustic devices to measure standoff distance, then the correction procedure can be performed, but the measurements become doubtful and inaccurate when vibration occurs due to the different position of resistivity sensor and caliper
Solution Approach 1:
The patent combines the resistivity sensor and standoff measurement function into a single integrated sensor assembly. The sensor includes a transmitter electrode and multiple return electrodes arranged in a concentric configuration, where the standoff distance is measured electrically through impedance measurements between the electrodes, eliminating the need for separate mechanical or acoustic measurement devices and ensuring consistent measurements regardless of vibration.
Solution Approach 2:
The patent replaces mechanical or acoustic standoff measurement devices with an electrical measurement system. By using alternating current voltage applied between the transmitter electrode and return electrodes, and measuring the resulting current to calculate impedance, the system substitutes mechanical/acoustic measurement with electrical measurement, providing more reliable standoff distance data even in vibrating conditions.
2Adaptability or versatility
If a single fixed-size electrode is used for resistivity measurement, then the sensor structure is simple, but the ability to compensate for variable standoff distances and maintain imaging resolution is limited
Solution Approach 1:
The patent segments the return electrode into multiple concentric rings with different radial dimensions. This segmentation allows the sensor to effectively measure standoff distance by analyzing impedance variations between the transmitter electrode and different return electrode rings, enabling compensation for variable standoff distances while maintaining imaging resolution.
Solution Approach 2:
The patent creates a dynamic measurement system where the effective return electrode size can be varied by selectively activating different concentric return electrode rings. This dynamic configuration allows the sensor to adapt to different standoff distances by choosing appropriate electrode combinations, improving standoff compensation capability without requiring a completely complex redesign.
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 system achieves accurate resistivity imaging with 360-degree coverage, effectively correcting for standoff variations and maintaining resolution, even in challenging environments like oil-based mud, by using variable-sized electrodes and multi-frequency measurements.
Implementation Method 1
measuring effective impedance for each of the currents; and estimating the property using the measurements of the effective impedance for each of the currents
Implementation Method 2
injecting a first current of a first frequency into the formation by applying an alternating current voltage between first selected ones of the plurality of return electrodes and the at least one transmitter electrode
Data Source
AI summary
Disclosed is a method of estimating a property of an earth formation penetrated by a borehole. The method includes conveying a carrier through the borehole and performing a plurality of electrical measurements on the formation using a sensor disposed at the carrier and having a plurality of electrodes disposed in a concentric arrangement wherein a standoff distance between the sensor and a wall of the borehole has an influence on each electrical measurement in the plurality of electrical measurements. The method further includes determining an impedance for each electrical measurement in the plurality of electrical measurements and inputting the determined impedances into an artificial neural network implemented by a processor. The artificial neural network outputs the property wherein the outputted property compensates for the influence of sensor standoff distance on each electrical measurement in the plurality of electrical measurements.