Tilted Coil Logging Tool Coupling Tensor Measurement
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Solution Overview
Problem
Conventional well logging tools face challenges in accurately measuring the entire electromagnetic coupling tensor of earth formations due to coil efficiency and electronic drift issues, which affect gain corrections and limit the characterization of conductivity anisotropy and boundary detection.
Innovation Solution
A logging tool system with a rotation axis and tilted transmitter and receiver coils measures coupling signals at multiple angles to determine the entire coupling tensor, allowing for gain-corrected measurements with a minimum number of coils, enabling comprehensive characterization of earth formation properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple transmitter and receiver coils with magnetic moments in multiple directions are used to measure the entire coupling tensor, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The tool is segmented into multiple independent coil assemblies (first and second transmitter coils, first and second receiver coils) with specific orientations. Each coil assembly can be independently controlled and measured, allowing the complex coupling tensor to be broken down into manageable components through systematic measurement of each coil pair's interaction.
Solution Approach 2:
The invention transitions from conventional single-dimension (z-axis only) induction logging to a multi-dimensional measurement system by introducing coils with magnetic moments in x and y directions as well as z direction. This dimensional expansion enables complete characterization of the coupling tensor, which has nine independent components, providing full spatial information about formation conductivity anisotropy.
2Device complexity
If conventional induction tools with z-directed coils only are used, then device complexity is reduced, but measurement precision is insufficient for complete coupling tensor characterization
Solution Approach 1:
The tool is segmented into multiple independent coil assemblies (first and second transmitter coils, first and second receiver coils) with specific orientations. Each coil assembly can be independently controlled and measured, allowing the complex coupling tensor to be broken down into manageable components through systematic measurement of each coil pair's interaction.
Solution Approach 2:
The invention transitions from conventional single-dimension (z-axis only) induction logging to a multi-dimensional measurement system by introducing coils with magnetic moments in x and y directions as well as z direction. This dimensional expansion enables complete characterization of the coupling tensor, which has nine independent components, providing full spatial information about formation conductivity anisotropy.
3Ease of operation
If coil efficiency and electronic drift are not corrected, then ease of operation is maintained, but measurement precision deteriorates due to inaccurate coupling tensor components
Solution Approach 1:
The system incorporates self-calibration through feedback measurements. By measuring the coupling between coils in known configurations and comparing against expected values, the system can identify and correct for coil efficiency variations and electronic drift. This feedback mechanism allows the tool to automatically adjust measurements, maintaining precision without requiring manual intervention or complex external calibration equipment.
Solution Approach 2:
The tool performs self-calibration by using its own coil interactions to determine and correct for gain variations. The measurement of coupling tensor components provides the feedback needed to compute correction factors that compensate for coil efficiency and electronic drift, allowing the system to correct its own measurements without external reference standards or complex calibration procedures.
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 accurate, gain-corrected determination of all components of the coupling tensor, improving the characterization of earth conductivity anisotropy and distance to boundaries, enhancing the precision of formation evaluation.
Implementation Method 1
energizing the transmitter coil (T coil) in the x-direction and measuring with a receiver coil (R coil) that is in the y-direction provides the xy-component of the coupling tensor
Data Source
AI summary
A system and method to determine earth formation properties by positioning a logging tool within a wellbore in the earth formation, the logging tool having a tool rotation axis and a first, a second, and a third tilted transmitter coil, and a tilted receiver coil; rotating the logging tool about the tool rotation axis; energizing each transmitter coil; measuring a coupling signal between each transmitter coil and the receiver coil for a plurality of angles of rotation; determining a coupling tensor; and determining the earth formation properties using the coupling tensor.