Azimuthal Resistivity Tool Eccentricity Correction
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Solution Overview
Problem
Azimuthal propagation resistivity tools face challenges in accurately measuring formation resistivity due to tool eccentricity and asymmetric mud invasion in deviated or horizontal boreholes, leading to unwanted signal interference and inaccurate measurements.
Innovation Solution
A method and apparatus that utilize both azimuthally-independent and azimuthally-sensitive resistivity measurements to estimate formation properties, correcting for tool eccentricity effects by using a combination of measurements from a logging tool, including a bucking coil and processor-based algorithms to isolate formation signals from eccentricity-induced noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of information
If an APR tool is used to detect azimuthal variations in resistivity, then directional information about formations ahead of the tool is provided, but the tool eccentricity from the borehole center axis causes unwanted signal interference and inaccurate measurements
Solution Approach 1:
The tool response is segmented into independent components: a formation-related signal and an eccentricity-induced signal. By separating these components through mathematical processing, the formation signal can be extracted without contamination from eccentricity effects, resolving the contradiction between obtaining directional information and maintaining measurement accuracy.
Solution Approach 2:
An intermediary processing system is introduced between the raw tool measurements and the final formation property estimates. This intermediary uses mathematical models and signal processing to eliminate eccentricity effects, allowing accurate formation resistivity measurements even when the tool is eccentric in the borehole.
2Object-affected harmful factors
If a bucking coil is used to minimize tool eccentricity effects, then some eccentricity cancellation is achieved, but significant eccentricity effects remain and additional processing complexity is required
Solution Approach 1:
The mechanical/electromagnetic bucking coil system is supplemented and enhanced by a mathematical processing system. Instead of relying solely on physical coil configurations to cancel eccentricity effects, the invention uses mathematical models and signal processing algorithms to remove eccentricity-induced signals from the measurements, reducing the burden on the physical coil design.
Solution Approach 2:
The invention changes the approach from physical parameter adjustment (coil configurations) to mathematical parameter adjustment. By using mathematical models to represent eccentricity effects and processing measurements accordingly, the system achieves more effective eccentricity cancellation without proportionally increasing physical device complexity.
3Adaptability or versatility
If measurements are taken in deviated or horizontal boreholes, then well placement and reservoir navigation are enabled, but asymmetric mud invasion and tool eccentricity induce additional unwanted signals
Solution Approach 1:
The mathematical processing system is designed to be universally applicable across different borehole configurations (vertical, deviated, horizontal). The same processing algorithms work regardless of borehole orientation, allowing the tool to maintain measurement accuracy while adapting to various well trajectories and navigation requirements.
Solution Approach 2:
The system uses feedback from the measurements themselves to identify and correct eccentricity effects. By analyzing the signal characteristics and comparing them against mathematical models, the system dynamically adjusts the processing to remove unwanted signals, maintaining accuracy across different borehole geometries.
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 solution effectively reduces the impact of tool eccentricity on resistivity measurements, providing more accurate directional information and formation property estimates, even in complex borehole geometries.
Implementation Method 1
An MPR tool typically includes transmitter coils and receiver coils having magnetic moments oriented parallel to and coincident with the tool axis
Implementation Method 2
the bucking coil works effectively in canceling a field that is directly coupled from the transmitter coil to the receiver coils
Data Source
AI summary
A method of evaluating an earth formation is disclosed which includes conveying a logging tool into a borehole in the earth formation and using the logging tool to obtain a first set of azimuthally-independent resistivity measurements of the earth formation and a second set of azimuthally-sensitive resistivity measurements of the earth formation and estimating a value of a property of the earth formation using the first set of measurements and the second set of measurements, the estimation being substantially unaffected by a displacement of the logging tool from a center of the borehole.